Semiconductor nanoparticles, production method for semiconductor nanoparticles, and light emitter

Abstract

Semiconductor nanoparticles 10 having a core-shell structure in which a coating layer 12 containing an In component as a main component is formed on the surface of a core particle 11 formed from a compound semiconductor having an Ag component, a Ge component, and a S component as main components.

Description

Semiconductor nanoparticles, method for producing semiconductor nanoparticles, and light emitter

[0001] The present invention relates to semiconductor nanoparticles, a method for producing semiconductor nanoparticles, and a light-emitting body, and more specifically to semiconductor nanoparticles having a core-shell structure in which a coating layer is formed on the surface of a core particle formed of a compound semiconductor containing Ag, Ge, and S as main components, a method for producing the same, and a light-emitting body containing the semiconductor nanoparticles.

[0002] Compound semiconductors, which are made by combining two or more different elements, have attracted attention because of their diverse properties. In particular, semiconductor nanoparticles, which are made by nanoparticleizing compound semiconductors, are now essential materials for luminescent materials, and various beneficial properties can be obtained by varying the element content ratio or by ultra-fine-particleizing them to 10 nm or less to exhibit quantum size effects. From this perspective, active research and development is being conducted on these semiconductors, with the aim of applying them to various fields, such as consumer, medical, and healthcare pharmaceuticals.

[0003] For example, Non-Patent Document 1 describes the structure and properties of Qdot nanocrystals (Qdot is a trade name) manufactured by Thermo Fisher Scientific.

[0004] That is, Non-Patent Document 1 describes nanocrystals that have a core-shell structure in which the core is made of CdSe or CdTe and the shell is made of ZnS, and the surface of the ZnS is coated with a polymer compound containing a carboxylate group (-COO) (see Fig. 6.6.1 of the same document and the section "Structural Properties").

[0005] This paper describes that by controlling the core size of the nanocrystals, it is possible to obtain emission spectra with different peak wavelengths in the range of 525 to 800 nm, and that the smaller the particle size, the shorter the wavelength of the light emitted. Therefore, according to this paper, it is possible to obtain nanocrystals with various emission properties by varying the particle size even with the same composition (see Fig. 6.6.5, "Spectroscopic Properties" in the same paper).

[0006] Furthermore, Patent Document 1 proposes a light emitter formed of nanoparticles made of a compound semiconductor containing Ag, In, and Se components, which has a peak wavelength of emission intensity in the range of 700 nm to 1400 nm and a half-value width of the peak wavelength of 100 nm or less.

[0007] In Patent Document 1, a steep and sharp emission spectrum with a half-width of 100 nm or less is obtained in the near-infrared region of 700 nm to 1400 nm. Patent Document 1 obtains a light emitter that has good light transmittance particularly in the wavelength region of 700 to 1000 nm, which is known as the "biological window," and attempts to obtain a light emitter suitable as a labeling agent (biomarker) for biological substances that constitute living organisms.

[0008] Furthermore, Patent Document 2 proposes a light-emitting body containing nanoparticles made of a compound semiconductor containing at least an Ag component, an In component, and a Se component, in which a hydrophilic coating is formed on the surface of the nanoparticles and the nanoparticles are dispersed in water, and the light-emitting body has a peak wavelength of emission intensity in the range of 650 nm to 1000 nm and a half-value width at the peak wavelength of 100 nm or less.

[0009] In Patent Document 2, the light emitter is dispersed in water with the nanoparticle surface made hydrophilic, so that nonpolar organic solvents that are harmful to cells are not adsorbed onto biological tissue, and a steep, sharp emission spectrum with a half-width of 100 nm or less is obtained in the near-infrared region of 650 nm to 1000 nm. Moreover, in Patent Document 2, a coating is formed on the surface of the nanoparticle to inactivate the surface, thereby achieving an emission quantum yield of 10% or more.

[0010] International Publication No. WO 2017 / 126164 (Claim 1, paragraph

[0033] , Table 1, etc.) International Publication No. WO 2020 / 246297 (Claim 1, 3, paragraph

[0024] , Table 1, etc.)

[0011] "Qdot Nanocrystals - Section 6.6", [online], Thermo Fisher Scientific, Inc., [Retrieved February 15, 2024], Internet <URL: https: / / www.thermofisher.com / jp / ja / home / references / molecular-probes-the-handbook / ultrasensitive-detection-technology / qdot-nanocrystal-technology.html>

[0012] However, Non-Patent Document 1 contains a Cd component, which is known as a harmful substance, in the core material that constitutes the nanocrystals, which places a heavy burden on the environment and makes it difficult to apply to various fields, including the biomedical field.

[0013] In contrast, Patent Documents 1 and 2 disclose nanoparticles made of compound semiconductors containing Ag, In, and Se components but not Cd components, but there is room for improvement in terms of further improving the luminescence quantum yield.

[0014] Furthermore, Patent Documents 1 and 2 contain an inherently toxic Se component. That is, although Se constitutes part of enzymes and proteins in the body and acts as an antioxidant, it is toxic and can cause poisoning symptoms if taken in chronic excess, so it must be managed and handled as a poison.

[0015] In recent years, it has been confirmed that In components are toxic, and it is desirable to limit their use as much as possible. However, this does not mean that they cannot be used in practical fields such as consumer products, medical and healthcare chemicals, etc.

[0016] The present invention has been made to solve the above problems, and aims to provide semiconductor nanoparticles with a high luminescence quantum yield, a method for producing the semiconductor nanoparticles, and a light-emitting material that can be used to apply the semiconductor nanoparticles to various fields such as consumer products, medical care, and healthcare pharmaceuticals.

[0017] The semiconductor nanoparticles of the present invention have a core-shell structure in which a coating layer containing an In component as a main component is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components.

[0018] The method for producing semiconductor nanoparticles of the present invention is a method for producing semiconductor nanoparticles having a core-shell structure in which a coating layer is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components, and the method includes the steps of: preparing an Ag-Ge-S mixed solution in which an Ag compound, a Ge compound, and an S compound are dissolved in a solvent; and heating the Ag-Ge-S mixed solution to produce a core particle made of a compound semiconductor; and adding the core particle made of the compound semiconductor and a plurality of raw material-containing compounds C1 including an In compound to a solvent to prepare a mixed solution M1; and heating the mixed solution M1 to 70°C or higher to cause a reaction.

[0019] The luminescent body of the present invention contains the semiconductor nanoparticles of the present invention.

[0020] According to the present invention, it is possible to provide semiconductor nanoparticles having a high luminescence quantum yield, a method for producing the semiconductor nanoparticles, and luminescent materials that can be used to produce semiconductor nanoparticles and are applicable to a variety of fields, such as consumer products, medical care, and healthcare pharmaceuticals.

[0021] FIG. 1 is a schematic diagram showing semiconductor nanoparticles according to an embodiment of the present invention. FIG. 2 is a TEM image of a sample of Example 1. FIG. 3 is a diagram showing absorption spectral profiles for each sample of Examples 1-2 and Comparative Examples 1-2. FIG. 4 is a diagram showing emission spectral profiles for each sample of Example 1 and Comparative Examples 1-2. FIG. 5 is a diagram showing emission spectral profiles for each sample of Examples 1-2 and Comparative Example 1. FIG. 6 is a diagram showing emission spectral profiles for a sample of Example 9. FIG. 7 is a diagram showing an XRD diffraction pattern for a sample of Example 5. FIG. 8 is a diagram showing absorption spectral profiles for each sample of Examples 1 and 5 and Comparative Examples 1-2.

[0022] The semiconductor nanoparticles, the method for producing semiconductor nanoparticles, and the light-emitting body of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope that does not change the gist of the present invention. Note that a combination of two or more of the individual desirable configurations described below also falls within the scope of the present invention.

[0023] The present inventors have conducted extensive research into compound semiconductors containing Ag, Ge, and S as their main components, which are relatively easy to handle and highly safe, and have found that by forming a coating layer containing In as its main component on the surface of core particles formed from this compound semiconductor, it is possible to obtain semiconductor nanoparticles with a high luminescence quantum yield (the proportion of photons emitted by luminescence among photons absorbed by the nanoparticles).

[0024] The present invention has been made based on this finding, and the semiconductor nanoparticles according to the present invention are characterized in that a coating layer containing an In component as a main component is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components, thereby forming a core-shell structure.

[0025] This makes it possible to obtain semiconductor nanoparticles with a high luminescence quantum yield.

[0026] FIG. 1 is a schematic diagram showing semiconductor nanoparticles according to an embodiment of the present invention.

[0027] The semiconductor nanoparticle 10 shown in FIG. 1 has a core-shell structure in which a coating layer (shell layer) 12 containing an In component as a main component is formed on the surface of a core particle 11 formed of a compound semiconductor containing Ag, Ge, and S components as main components (hereinafter referred to as an "Ag-Ge-S-based compound semiconductor").

[0028] Conventionally, a stoichiometric composition containing Ag, Ge, and S components has been used. ８ GeS ６These component elements do not require strict control like Cd, and are safe and easy to handle. Therefore, semiconductor nanoparticles formed from Ag—Ge—S-based compound semiconductors are promising as a substitute for CdSe.

[0029] In recent years, semiconductor nanoparticles of this type have been attracting attention for their application as biomarkers for biosubstances that constitute living organisms.

[0030] However, conventional semiconductor nanoparticles formed from Ag--Ge--S compound semiconductors do not have a sufficiently high luminescence quantum yield, and increasing their luminescence intensity has been a challenge.

[0031] That is, when photon energy is applied to the Ag—Ge—S-based compound semiconductor serving as the core particle 11, the Ag—Ge—S-based compound semiconductor absorbs the light, and electrons in the ground state valence band are excited to the conduction band, forming holes in the valence band. The excited electrons are then attracted by Coulomb force to the ground state valence band where holes exist, and the electrons and holes recombine to emit light.

[0032] However, the Ag—Ge—S-based compound semiconductor serving as the core particle 11 is an ultrafine particle with an average particle size on the order of nanometers, and a large number of atoms are present on the particle surface of the compound semiconductor. Therefore, many defects exist in the crystal structure of the surface of the Ag—Ge—S-based compound semiconductor serving as the core particle 11. These defects form various energy levels, i.e., defect levels, between bands. Therefore, when electrons excited by light absorption transition from the conduction band to the valence band, the excited electrons return to the valence band while undergoing vibrational relaxation without emitting light due to the defect levels. This can lead to non-radiative deactivation, in which electrons that transition to the valence band do not emit light even when they recombine with holes, potentially resulting in a deterioration of the luminescence characteristics. Therefore, to further improve the luminescence characteristics, it is necessary to reduce the surface defects of the core particle 11 and suppress non-radiative deactivation. To achieve this, it is considered preferable to form a coating layer (shell layer) 12 on the surface of the core particle 11 to seal the surface defects.

[0033] However, if the upper end of the band gap energy of the shell material forming the coating layer 12 is lower than the lower end of the band gap energy (lower end of the conduction band) of the core particle 11, the excited electrons will transition from the conduction band to a low energy level at the upper end of the band gap of the shell material, and then from this low energy level to the ground state valence band, resulting in a loss of light emission from the core particle 11.

[0034] Therefore, it is necessary to avoid the loss of luminescence from core particle 11 by forming coating layer 12 as a layer having a band gap energy larger than the band gap energy of core particle 11. In this embodiment, by using a compound containing In as a main component, in particular, as the shell material for forming coating layer 12, it is possible to effectively seal surface defects of core particle 11, thereby effectively reducing non-radiative deactivation, thereby suppressing energy loss and enabling improvement of luminescence characteristics. More specifically, it is possible to achieve a high luminescence quantum yield and significantly improve luminescence intensity.

[0035] For example, a typical crystalline phase containing In is In ２ S ３ The band gap energy of Ag-Ge-S compound semiconductor is about 2.1 eV, and Ag ８ GeS ６ Since the band gap energy is wider than the band gap energy (about 1.45 eV) of SiO 2 , it is believed that the surface defects can be effectively blocked and non-radiative deactivation can be effectively reduced.

[0036] In the semiconductor nanoparticles, the content ratio converted into the molar ratio of the Ag component to the Ge component (hereinafter referred to as the "content molar ratio Ag / Ge") is not particularly limited and can be set appropriately depending on the application, etc., but is preferably 1.0 or more and less than 7.5.

[0037] In recent years, this type of semiconductor nanoparticle has attracted attention for its application as a labeling agent (biomarker) for biological substances constituting living organisms. In this case, it has traditionally been considered preferable to generate fluorescence in the near-infrared region of 700 to 1700 nm. That is, in the visible light region of 400 nm to less than 700 nm, which has shorter wavelengths than the near-infrared region, absorption by biological constituents such as hemoglobin is high. Furthermore, as wavelengths increase beyond 1700 nm, absorption by water increases, making it difficult for light to penetrate efficiently within living organisms. In contrast, the near-infrared region of 700 to 1700 nm, particularly the region of 700 to 1000 nm, has high optical transparency within living organisms and is considered a wavelength range suitable for the application of bioimaging technology.

[0038] However, the stoichiometric composition of Ag—Ge—S based compound semiconductors is Ag as described above. ８ GeS ６ The stoichiometric ratio of the Ag / Ge molar ratio is "8". ８ GeS ６ The absorption edge wavelength of is approximately 900 nm, and therefore the emission wavelength, particularly the maximum wavelength, may exceed 1000 nm, which may make it difficult to obtain highly accurate biological information even when irradiating biological tissue.

[0039] That is, when photon energy is applied to this type of semiconductor nanoparticle, the semiconductor nanoparticle absorbs light, and electrons in the ground state valence band are excited to the conduction band, forming holes in the valence band. The excited electrons are then attracted to the ground state valence band where holes exist by Coulomb force, and the electrons and holes recombine to emit light. In this case, in order to achieve high-efficiency light emission, it is preferable to make the emission wavelength as close as possible to the absorption edge wavelength. However, when electrons return from the excited state to the valence band, part of the photon energy is usually consumed as vibrational energy, etc., resulting in a shift called the Stokes shift between the absorption wavelength and the emission wavelength. Therefore, the emission wavelength of the semiconductor nanoparticle is longer than the absorption edge wavelength. However, with a stoichiometric ratio of Ag / Ge content of "8", the absorption edge wavelength is about 900 nm as described above, so the emission wavelength, especially its maximum wavelength, may exceed 1000 nm. Even when irradiated to biological tissue, the light transmittance in the living body is poor, which may make it difficult to obtain highly accurate biological information.

[0040] On the other hand, when the molar ratio Ag / Ge is adjusted so that the molar amount of Ag contained is less than the stoichiometric ratio, the absorption edge wavelength can be shifted to the short wavelength side, to about 650 to 800 nm, and this makes it possible to emit light in the wavelength range of 700 to 1000 nm, which has good light transmittance to living organisms.

[0041] However, if the molar ratio Ag / Ge is less than 1.0, the Ag component will be extremely low, which may hinder the reaction for producing nanoparticles and make it impossible to obtain an Ag-Ge-S based compound semiconductor.

[0042] On the other hand, if the molar ratio Ag / Ge is 7.5 or more, the luminous efficiency may decrease.

[0043] Therefore, in this embodiment, the contents of the Ag component and the Ge component are adjusted so that the molar ratio Ag / Ge is preferably 1.0 or more and less than 7.5, and more preferably 1.8 or more and 7.3 or less.

[0044] The average particle size of the semiconductor nanoparticles is not particularly limited as long as it is on the order of nanometers (generally 1 to 100 nm), but is preferably 9 nm or less.

[0045] In other words, semiconductor nanoparticles that have been ultrafine-grained to an average particle size of approximately 10 nm or less generally exhibit a quantum size effect in which the band gap energy increases as the particle size decreases, and even when semiconductor materials with the same component composition are used, the light absorption and emission wavelengths can be controlled over a wide range.

[0046] Therefore, in this embodiment, it is preferable to control the average particle size of the semiconductor nanoparticles to 9 nm or less by adjusting reaction conditions such as reaction temperature and reaction time, which enables the quantum size effect to be exhibited, and by varying the average particle size, it becomes possible to vary the emission wavelength as needed within the wavelength range of 700 to 1000 nm.

[0047] Here, the average particle size refers to the arithmetic mean value of the equivalent circle diameter of each particle.

[0048] Furthermore, the standard deviation σ of the average particle size of the semiconductor nanoparticles is preferably suppressed to 3 nm or less, more preferably 1 nm or less.

[0049] This makes it possible to obtain stable, high-quality semiconductor nanoparticles with uniform particle size and good dispersibility.

[0050] In this embodiment, the coating layer 12 preferably further contains a Zn component as a main component.

[0051] This allows the luminescence quantum yield and luminescence intensity to be increased.

[0052] The Zn-containing compound may be an In-containing compound (e.g., the above-mentioned In ２ S ３ ), the band gap energy is larger than that of Zn. Therefore, by using Zn in combination as the shell material for forming the coating layer 12, it is thought that defect levels can be more effectively removed and the exciton confinement effect can be more effectively achieved, resulting in higher luminescence quantum yield and luminescence intensity.

[0053] For example, as described above, Ag—Ge—S compound semiconductors have a stoichiometric composition of Ag ８ GeS ６The band gap energy of In is about 1.45 eV, which is the typical crystal phase containing In. ２ S ３ Since the band gap energy of ZnS is about 2.1 eV, a typical crystalline phase containing Zn, ZnS, which has a band gap energy of about 3.7 eV, is suitable.

[0054] In this embodiment, it is preferable that the coating layer 12 further contains, as a main component, at least one element Z1 selected from the group of elements belonging to Group 16 of the periodic table.

[0055] This makes it possible to easily form the coating layer 12 containing the In component and the Zn component.

[0056] That is, the shell material for forming the coating layer 12 may be a compound containing In and at least one element Z1 selected from the group of elements belonging to Group 16 of the periodic table, or a compound containing Zn and at least one element Z1 selected from the group of elements belonging to Group 16 of the periodic table.

[0057] As the element Z1, at least one element selected from the group consisting of S and O can be used.

[0058] The In component and the Zn component may be present in different layers, or may be present in the same layer.

[0059] When the In component and the Zn component are present in different layers, a plurality of coating layers 12 are formed on the surface of the core particle 11. In this case, either the layer containing the In component or the layer containing the Zn component may be on the inner side. That is, the layers may be arranged in the order core particle / In-containing coating layer / Zn-containing coating layer from the center, or the layers may be arranged in the order core particle / Zn-containing coating layer / In-containing coating layer from the center.

[0060] It is also possible to form three or more coating layers.

[0061] When the In component and the Zn component are present in the same layer, only one layer may be formed as the coating layer 12 on the surface of the core particle 11. In this single coating layer 12, the In-containing compound and the Zn-containing compound may be in a mixed state or may be separated, for example, in a marble-like state.

[0062] In this embodiment, the coating layer 12 may further contain, as a main component, at least one element Z2 selected from the group of elements belonging to Group 11 of the periodic table. An example of the element Z2 is Ag. Specifically, the coating layer 12 may be AgInS ２ and AgInS as a crystalline phase containing Ag and In. ２ may also include:

[0063] In this way, the coating layer 12 may contain a compound containing In, the element Z1, and the element Z2.

[0064] As described above, according to the semiconductor nanoparticles of the present invention, a coating layer containing an In component as a main component is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components, and thus a core-shell structure is formed, and therefore semiconductor nanoparticles with a high luminescence quantum yield can be obtained.

[0065] Next, one embodiment of the method for producing semiconductor nanoparticles of the present invention will be described in detail.

[0066] First, to obtain a Ge compound as a Ge source, for example, a hydroxy acid is reacted with a Ge oxide. Here, the hydroxy acid is not particularly limited as long as it is a carboxylic acid containing a hydroxy group, and examples thereof include glycolic acid (HOCH ２ COOH), lactic acid (CH ３ CH(OH)COOH), malic acid (HOOCCH(OH)CH ２ COOH), glycerin (HOCH ２ CH(OH)COOH) can be used. There is no particular limitation on the Ge oxide, but germanium (IV) oxide (GeO ２ ) is preferred.

[0067] Then, predetermined amounts of hydroxy acid and Ge oxide are weighed out, and these weighed materials are mixed in highly pure water or ultrapure water. The mixture is heated and stirred in an oil bath adjusted to a predetermined temperature (e.g., 100°C), thereby causing a reaction between the hydroxy acid and the Ge oxide, and then the mixture is evaporated and dried to obtain a Ge compound.

[0068] Next, an Ag compound serving as an Ag source and an S compound serving as an S source are prepared. Here, the Ag compound is not particularly limited, and for example, silver N,N-diethyldithiocarbamate (AgS ２ CN (C ２ H ５ ) ２ ) (hereinafter referred to as "AgDDTC"), silver acetate (AgOCOCH ３ ), organic silver salts such as silver nitrate (AgNO ３ ), silver sulfate (Ag ２ SO ４ Inorganic silver salts such as thiourea (SC(NH)) can be used as the sulfur compound. ２ ) ２ ) can be used.

[0069] The Ag compound, Ge compound, and S compound are then weighed out so that the molar ratio Ag / Ge in the final product semiconductor nanoparticles is preferably 1.0 or more and less than 7.5, more preferably 1.8 or more and 7.3 or less.

[0070] Next, these weighed materials are dissolved in a solvent to prepare an Ag-Ge-S mixed solution. Here, as the solvent, a high-boiling solvent that has a boiling point higher than the reaction temperature described below and is chemically stable can be preferably used, and for example, a mixed solution of high-boiling aliphatic amines and fat-soluble thiols can be used. Here, as the aliphatic amines, hexylamine (C ６ H １３ NH ２ ), heptylamine (C ７ H １５ NH ２ ), octylamine (C ８ H １７ NH ２ ), nonylamine (C ９ H １９ NH２ ), decylamine (C １０ H ２１ NH ２ ), dodecylamine (C １２ H ２５ NH ２ ), tetradecylamine (C １４ H ２９ NH ２ ), pentadecylamine (C １５ H ３１ NH ２ ), hexadecylamine (C １６ H ３３ NH ２ ), heptadecylamine (C １７ H ３５ NH ２ ), octadecylamine (C １８ H ３７ NH ２ ), oleylamine (C ８ H １７ CH=CHC ８ H １６ NH ２ Among these aliphatic amines, oleylamine, which is liquid at room temperature and has a high boiling point of about 350° C., can be particularly preferably used.

[0071] As the fat-soluble thiol, an aliphatic thiol, a dithiol, or an aromatic thiol can be used. Among these fat-soluble thiols, 1-dodecanethiol (C ) having a high boiling point of about 270°C is particularly preferred. １２ H ２５ SH) can be particularly preferably used.

[0072] Next, the Ag-Ge-S mixed solution is degassed under reduced pressure and then substituted with nitrogen, followed by a heat treatment at a predetermined reaction temperature to cause a reaction and obtain a reaction product. Here, the reaction temperature is preferably 150°C or higher but lower than 250°C. That is, if the reaction temperature is lower than 150°C, the reaction temperature is too low and the particle generation reaction does not proceed easily. On the other hand, if the reaction temperature is higher than 250°C, particle growth is promoted, resulting in coarsening of the particles, which may make it difficult to obtain dispersed, stable nanoparticles.

[0073] Therefore, as described above, the reaction temperature is preferably 150°C or higher and lower than 250°C, and more preferably 150°C or higher and 220°C or lower.

[0074] The reaction time is not particularly limited, but can be set to, for example, about 5 to 20 minutes. Particle growth can also be controlled by changing the reaction time, thereby adjusting the particle size to within a range of 9 nm or less. By adjusting the average particle size in this way, the emission wavelength fluctuates due to the quantum size effect, allowing the peak wavelength of the emission intensity to be controlled.

[0075] Furthermore, by controlling the above-mentioned reaction conditions (reaction temperature and reaction time), the content molar ratio Ag / Ge can be adjusted. That is, even if the charged amounts of the Ag compound, the Ge compound, and the S compound are the same, it is possible to control not only the average particle size but also the content molar ratio Ag / Ge by changing the reaction conditions.

[0076] The reaction mixture is then left to cool to room temperature, and then centrifuged to separate it into a supernatant and a precipitate. The supernatant is collected and the precipitate is discarded. A poor solvent such as methanol, ethanol, acetone, or acetonitrile is then added to the supernatant to produce a precipitate, which is then centrifuged again to separate and collect the precipitate.

[0077] The procedure of adding a poor solvent, centrifuging, and recovering the precipitate is preferably repeated several times, thereby producing a highly pure precipitate that is free from impurities such as other phases.

[0078] Next, by dissolving this precipitate in a non-polar solvent such as chloroform, toluene, or hexane, the nanoparticles formed of the Ag-Ge-S compound semiconductor are stably dispersed in the non-polar solvent, thereby producing a nanoparticle dispersion solution.

[0079] Subsequently, a coating layer containing an In component is formed.

[0080] First, a predetermined amount of nanoparticles as core particles is collected from the nanoparticle dispersion and thoroughly degassed. A solvent such as oleylamine is heated and stirred while being degassed under vacuum, and then cooled to room temperature to prepare a dry solvent.

[0081] Next, a plurality of compounds C1 containing raw materials for forming the coating layer 12 are prepared.

[0082] As the raw material-containing compound C1, an In compound containing In and a Z1 compound containing at least one element Z1 selected from Group 16 of the periodic table to which S, O, etc. belong can be used.

[0083] As the Z1 compound, an S compound containing S can be preferably used.

[0084] Here, the In compound is not particularly limited, and examples thereof include indium acetate (In(OOCCH ３ ) ３ ), indium chloride (InCl ３ Inorganic acid salts of In, such as HCl, ...

[0085] Furthermore, the sulfur compound is thiourea (SC(NH ２ ) ２ ) can be preferably used.

[0086] Then, predetermined amounts of the core particles and the above-described plurality of raw material-containing compounds C1 are weighed out, these weighed materials are mixed, and after nitrogen substitution, the above-described dry solvent is added as a solvent to obtain a mixed solution M1. Thereafter, this mixed solution M1 is subjected to a heat treatment at a reaction temperature of 70°C or higher for a predetermined time. This yields a reaction product (core-shell particles) in which a coating layer 12 containing an In component as a main component is formed on the surface of the core particles 11.

[0087] The reaction temperature is not particularly limited as long as it is 70°C or higher, but is preferably 70°C or higher but lower than 250°C, and more preferably 70°C or higher but lower than 220°C. If the reaction temperature is lower than 70°C, the reaction temperature is too low and the reaction to produce a coating layer containing an In component as a main component does not proceed easily. On the other hand, if the reaction temperature is higher than 250°C, the reaction is accelerated, resulting in coarsening of the particles, which may make it difficult to obtain dispersed, stable nanoparticles.

[0088] The reaction temperature may be 200° C. or higher, which results in AgInS ２ On the other hand, the reaction temperature may be lower than 200° C., and in this case, the coating layer 12 made of In ２ S ３ The coating layer 12 can be formed by

[0089] The reaction time is not particularly limited, but can be set to, for example, about 5 to 30 minutes.

[0090] The core particles contained in the mixed solution M1 may be core particles whose surfaces have been coated in advance with some kind of coating layer (for example, a coating layer containing Zn as a main component), that is, core-shell particles.

[0091] Next, the reaction mixture is left to cool for a predetermined time, and then centrifuged to separate the mixture into a supernatant and a precipitate, using substantially the same method and procedure as above, in order to remove coarse particles. The supernatant is collected and the precipitate is discarded. A poor solvent such as methanol, ethanol, acetone, or acetonitrile is then added to the supernatant to produce a precipitate, which is then centrifuged again, the supernatant is discarded, and the precipitate is separated and collected.

[0092] It is preferable to repeat the procedure of adding a poor solvent, centrifuging, and recovering the precipitate multiple times, as described above, thereby removing coarse particles and producing an ultrafine precipitate that does not contain impurities such as heterogeneous phases.

[0093] Next, this precipitate is dried in the air and then dissolved in a non-polar solvent such as chloroform, toluene, or hexane, whereby the semiconductor nanoparticles having a core-shell structure are stably dispersed in the non-polar solvent, thereby producing the nanoparticle dispersion solution (core-shell particle dispersion solution) according to this embodiment.

[0094] When a coating layer containing a Zn component is formed, the following steps are further carried out.

[0095] The following steps may be performed before or after the step of forming the coating layer containing an In component.

[0096] First, a predetermined amount of core-shell particles is taken from the core-shell particle dispersion and thoroughly degassed. Alternatively, a predetermined amount of core particles is taken from the nanoparticle dispersion before the formation of the coating layer containing an In component and thoroughly degassed. Furthermore, a solvent such as oleylamine is heated and stirred under vacuum while being degassed, and then cooled to room temperature to prepare a dry solvent.

[0097] Next, a plurality of compounds C2 containing raw materials for forming the coating layer 12 are prepared.

[0098] As the raw material-containing compound C2, a Zn compound containing Zn and a Z1 compound containing at least one element Z1 selected from Group 16 of the periodic table to which S, O, etc. belong can be used.

[0099] As the Z1 compound, an S compound containing S can be preferably used.

[0100] Here, the Zn compound is not particularly limited, and examples thereof include zinc acetate (Zn(CH ３ COO) ２ ), zinc chloride (ZnCl ２ ), zinc nitrate (Zn(NO ３ ) ２ ), zinc iodide (ZnI ２ ), inorganic salts of Zn such as zinc oleate (Zn(C ８ H １７ CH=CHC ７ H14COO) ２ ), zinc myristate (Zn(C １３ H ２７ COO) ２ ) and other Zn fatty acid salts can be used, and bis(2,4-pentanedionato)zinc(II) represented by the chemical formula (1) can be preferably used.

[0101]

[0102] Furthermore, the sulfur compound is thiourea (SC(NH ２ ) ２ ) can be preferably used.

[0103] Then, predetermined amounts of the core-shell particles (or core particles) and the above-described plurality of raw material-containing compounds C2 are weighed out, these weighed materials are mixed, and after nitrogen substitution, the above-described dry solvent is added as a solvent to obtain a mixed solution M2. Thereafter, this mixed solution M2 is subjected to a heat treatment at a predetermined reaction temperature for a predetermined time. This yields a reaction product (core-shell particles) in which a coating layer 12 containing a Zn component as a main component is formed on the surface of the core particle 11.

[0104] Here, the reaction temperature is not particularly limited, but is preferably 50°C or higher and 200°C or lower, and more preferably 70°C or higher and 200°C or lower. If the reaction temperature is lower than 50°C, the reaction temperature is too low and the reaction to form a coating layer containing Zn as a main component does not proceed easily. On the other hand, if the reaction temperature is higher than 250°C, the reaction is accelerated, resulting in coarsening of the particles, which may make it difficult to obtain dispersed, stable nanoparticles.

[0105] The reaction time is not particularly limited, but can be set to, for example, about 5 to 30 minutes.

[0106] Next, the reaction mixture is left to cool for a predetermined time, and then centrifuged to separate the mixture into a supernatant and a precipitate, using substantially the same method and procedure as above, in order to remove coarse particles. The supernatant is collected and the precipitate is discarded. A poor solvent such as methanol, ethanol, acetone, or acetonitrile is then added to the supernatant to produce a precipitate, which is then centrifuged again, the supernatant is discarded, and the precipitate is separated and collected.

[0107] It is preferable to repeat the procedure of adding a poor solvent, centrifuging, and recovering the precipitate multiple times, as described above, thereby removing coarse particles and producing an ultrafine precipitate that does not contain impurities such as heterogeneous phases.

[0108] Next, this precipitate is dried in the air and then dissolved in a non-polar solvent such as chloroform, toluene, or hexane, whereby the core-shell structured semiconductor nanoparticles are stably dispersed in the non-polar solvent, thereby producing a core-shell particle dispersion solution in which the coating layer 12 contains a Zn component.

[0109] The core-shell structure of the semiconductor nanoparticles of the present invention can be confirmed by performing a compositional analysis to detect the components of the shell material, and then observing the core particle 11 alone and the core-shell structure of the semiconductor nanoparticles of the present invention under an electron microscope and comparing the average particle diameters. The core-shell structure can also be confirmed by performing elemental analysis at regular intervals linearly from the edge of the prepared semiconductor nanoparticles using an electron microscope. That is, in semiconductor nanoparticles with a core-shell structure, a large amount of shell components is detected near the edge, and a large amount of core components is detected near the center, so the core-shell structure can also be confirmed by such elemental analysis. Furthermore, the core-shell structure can also be estimated by comparing the absorption spectra of the core particle 11 alone and the core-shell structure of the semiconductor nanoparticles of the present invention.

[0110] As described above, the method for producing semiconductor nanoparticles of the present invention includes the steps of preparing an Ag-Ge-S mixed solution in which an Ag compound, a Ge compound, and an S compound are dissolved in a solvent, and heating the Ag-Ge-S mixed solution to produce core particles made of a compound semiconductor, and adding the core particles made of the compound semiconductor and a plurality of raw material-containing compounds C1 including an In compound to a solvent to prepare a mixed solution M1, and heating the mixed solution M1 to 70°C or higher to cause a reaction. Therefore, it is possible to easily obtain semiconductor nanoparticles with a core-shell structure in which a coating layer containing an In component as a main component is formed on the surface of core particles made of an Ag-Ge-S based compound semiconductor.

[0111] Furthermore, since the light-emitting body containing the semiconductor nanoparticles of the present invention can emit light in the near-infrared region with a wavelength of 700 to 1000 nm, it can be suitably applied to bioimaging technology as a labeling agent (biomarker) for biological substances. That is, the light-emitting body containing the semiconductor nanoparticles of the present invention can be adsorbed onto biological tissue, irradiated with near-infrared light to cause the light-emitting body to emit light, and the image can be dynamically analyzed to detect biological information, making it possible to efficiently confirm the effectiveness of medication and the state of cells in regenerative medicine, cancer treatment, etc.

[0112] Furthermore, the luminescent material containing the semiconductor nanoparticles has high luminescence quantum yield and luminescence intensity, and therefore can be observed more clearly as a labeling agent for biological substances. Alternatively, since the function as a labeling agent for biological substances can be ensured even when the amount of the semiconductor nanoparticles used is reduced, it is also possible to use the semiconductor nanoparticles as a labeling agent for biological substances while reducing the amount of In component, the use of which is desirably limited as much as possible.

[0113] The semiconductor nanoparticles of the present invention do not exclude substances that are inevitably mixed in during the manufacturing process, and may contain any additives as long as they do not affect the properties.

[0114] Furthermore, the light-emitting body of the present invention can be used not only as a labeling agent for biological substances as described above, but also as a light source for exciting markers in vivo. For example, by filling the sealing portion of a blue light-emitting diode or an ultraviolet light-emitting diode with the semiconductor nanoparticles of the present invention, the semiconductor nanoparticles of the present invention can be excited by the blue light-emitting diode or the ultraviolet light-emitting diode to emit light in the near-infrared region of 700 to 1400 nm, and can be used as light in this wavelength region to excite markers in vivo.

[0115] Furthermore, the semiconductor nanoparticles of the present invention can also be used as a sensitizing filter that increases the sensitivity of a night-vision camera, and can contribute to improving the sensitivity of the night-vision camera.

[0116] Examples will be given below that more specifically disclose the semiconductor nanoparticles, the method for producing semiconductor nanoparticles, and the light emitter of the present invention, but the present invention is not limited to these examples.

[0117] [Sample Preparation] (Comparative Example 1) First, germanium glycolate (Ge(OCH ２ COO) ２ (H ２ O) ２ Specifically, glycolic acid with a purity of 97% (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and germanium (IV) oxide with a purity of 99.99% (manufactured by Kojundo Chemical Research Institute Co., Ltd.) were prepared.

[0118] Then, 1.25 g of glycolic acid and 0.5 g of germanium (IV) oxide were weighed out, and these weighed amounts were added to 25 cm of ultrapure water. ３ The mixture was placed in a three-neck flask together with a stirrer chip, and heated in an oil bath at 100°C for 1 hour while stirring with a magnetic stirrer to obtain a colorless, transparent mixed solution. This mixed solution was then evaporated and dried to obtain germanium glycolate.

[0119] Next, AgDDTC (manufactured by Dojindo Laboratories) was prepared as an Ag source, thiourea (manufactured by Tokyo Chemical Industry Co., Ltd.) with a purity of 98% was prepared as an S source, and oleylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) with a purity of 50% and 1-dodecanethiol (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.) with a purity of 98% were prepared as solvents.

[0120] Then, 0.025 mmol of AgDDTC, 0.043 mmol of germanium glycolate, and 0.100 mmol of thiourea were placed in test tubes, and 2.75 cm of oleylamine was added to each test tube. ３ , 1-dodecanethiol 0.25 cm ３ were added together with a stirrer chip and stirred to prepare an Ag—Ge—S mixed solution.

[0121] Next, the inside of the test tube was degassed under reduced pressure, and then replaced with nitrogen gas. The mixture was heated at a reaction temperature of 150° C. for 20 minutes while stirring with a magnetic stirrer, thereby obtaining a black-brown suspension (reaction product).

[0122] The suspension was then air-cooled to room temperature and then centrifuged at 4,000 rpm for 5 minutes to separate the supernatant and the precipitate. The supernatant was collected and the precipitate was discarded. Next, 3 cm of methanol was added to the collected supernatant. ３ The mixture was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３The mixture was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. The precipitate was then redispersed in chloroform (purity 99%, Kishida Chemical Co., Ltd.) as a nonpolar solvent to prepare a sample of Comparative Example 1 (a dispersion of Ag-Ge-S nanoparticles).

[0123] After the solvent was dried off, the sample of Comparative Example 1 was subjected to a composition analysis using a scanning electron microscope-energy dispersive X-ray analyzer (hereinafter referred to as "SEM-EDX") (manufactured by Horiba, Ltd., EMAX Energy). The composition formula was Ag ５０．５ Ge ９．２ S ４０．３ It was.

[0124] (Example 1) A sample (Ag—Ge—S nanoparticle dispersion solution) prepared in the same manner as in Comparative Example 1 was placed in a test tube in an amount of 1.6 nmol of particles, and the solvent was dried overnight under reduced pressure. The number of particles was determined based on the molar absorption coefficient of the nanoparticles, 5.34 × 10 ６ The particle concentration was calculated from the absorbance measurement results of the nanoparticle dispersion solution using the HPLC method (L / (mol cm@365 nm) (L is liters)), and the nanoparticle dispersion solution equivalent to the required number of particles was taken.

[0125] In this specification, the absorbance of the sample (calculation of the sample concentration) and the light absorption characteristics of the sample were measured by measuring the absorption spectrum using a diode array spectrophotometer (8453a manufactured by Agilent Technologies).

[0126] After drying, 0.0073 mmol (=2.13 mg) of indium acetate (MW=291.95) and 0.0073 mmol (=0.55 mg) of thioacetamide (MW=75.13) were added to the test tube as a shell (coating layer) precursor, i.e., a compound C1 containing a plurality of raw materials. A stirrer was placed in the test tube containing the core particles and the compound C1 containing a plurality of raw materials, and the atmosphere was replaced with nitrogen. Then, 3 cm of dried oleylamine was injected into the test tube using a syringe. ３ Mixture M1 was obtained.

[0127] The dried oleylamine was obtained by heating and stirring 50% pure oleylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) at 100°C for 1 hour while degassing under reduced pressure, and then air-cooling it to room temperature.

[0128] Then, the test tube containing the mixed solution M1 was heated and stirred with a hot stirrer at a reaction temperature of 110° C. for 15 minutes.

[0129] After heating, the test tube was left to cool at room temperature for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate. The supernatant was then passed through a 0.20 μm membrane filter and recovered. No precipitate was formed. Next, 3 cm of methanol was added to the recovered supernatant. ３ The resulting precipitate was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３ The resulting precipitate was dried at room temperature for 10 minutes, and then 3 cm of chloroform (purity 99%, Kishida Chemical Co., Ltd.) was added as a non-polar solvent. ３ The resulting mixture was re-dispersed in the Ag—Ge—S / InS core-shell particle dispersion solution to prepare the sample of Example 1.

[0130] After the solvent was dried, the sample of Example 1 was subjected to composition analysis using SEM-EDX, and the composition formula was found to be Ag ３０．７ Ge ６．３ S ４６．６ In １６．４ It was.

[0131] Example 2 A sample (Ag—Ge—S / InS core-shell particle dispersion solution) prepared in the same manner as in Example 1 was dried overnight in a vacuum desiccator. Since the amount of core particles prepared during core-shell particle synthesis was 1.6 nmol, if the core-shell particles were completely coated with an In-containing coating layer, this solution would also contain 1.6 nmol of core-shell particles.

[0132] After drying, 0.0094 mmol (=5.91 mg) of zinc stearate (MW=632.35) and 0.0094 mmol (=0.70 mg) of thioacetamide (MW=75.13) were added to the test tube as compound C2 containing multiple raw materials. A stirrer was placed in the test tube containing the core-shell particles and compound C2 containing multiple raw materials, and 3 cm of dried oleylamine was added using a syringe. ３ Mixture solution M2 was obtained.

[0133] The dried oleylamine was prepared in the same manner as in Example 1.

[0134] Then, after replacing the atmosphere with nitrogen, the test tube containing the mixed solution M2 was heated and stirred with a hot stirrer at a reaction temperature of 100° C. for 15 minutes.

[0135] After heating, the test tube was left to cool at room temperature for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate. The supernatant was then passed through a 0.20 μm membrane filter and recovered. No precipitate was formed. Next, 3 cm of methanol was added to the recovered supernatant. ３ The resulting precipitate was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３ The resulting precipitate was dried at room temperature for 30 minutes, and then 3 cm of chloroform (purity 99%, Kishida Chemical Co., Ltd.) was added as a non-polar solvent. ３ The particles were re-dispersed in the aqueous solution to prepare a sample of Example 2 (Ag-Ge-S / (InS.ZnS) core-shell particle dispersion solution).

[0136] Then, as in Example 1, the solvent was dried off from the sample of Example 2, and then composition analysis was carried out using SEM-EDX. The composition formula was found to be Ag ２４．０ Ge ４．２ S ４８．９ In ９．５ Zn ９．５ It was.

[0137] (Example 3) A sample of Example 3 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 70° C. Then, as in Example 1, the solvent of this sample of Example 3 was dried, and then a composition analysis was performed using SEM-EDX. ３７．５ Ge ７．５ S ４３．７ In １１．４ It was.

[0138] Example 4 A sample of Example 4 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 90° C. Then, as in Example 1, the solvent of this sample of Example 4 was dried, and then a composition analysis was performed using SEM-EDX. ３６．７ Ge ５．９ S ４５．０ In １２．４ It was.

[0139] Example 5 A sample of Example 5 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 200° C. Then, as in Example 1, the solvent of this sample of Example 5 was dried, and then a composition analysis was performed using SEM-EDX. ３５．２ Ge ６．０ S ４５．６ In １３．３ It was.

[0140] Example 6 A sample of Example 6 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 90° C. and the reaction time was set to 10 minutes. Then, after drying the solvent, the sample of Example 6 was subjected to composition analysis using SEM-EDX, as in Example 1. The composition formula was Ag ３７．５ Ge ７．５ S ４３．１ In １１．９ It was.

[0141] Example 7 A sample of Example 7 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 90° C. and the reaction time was set to 20 minutes. Then, as in Example 1, the solvent of this sample of Example 7 was dried, and then a composition analysis was performed using SEM-EDX. The composition formula was found to be Ag ３７．４ Ge ５．６ S ４５．２ In １１．９ It was.

[0142] Example 8 A sample of Example 8 was prepared in the same manner and procedure as in Example 1, except that the reaction temperature of the mixed solution M1 of the core particles and the compound C1 containing a plurality of raw materials was set to 90° C. and the reaction time was set to 30 minutes. Then, as in Example 1, the solvent of this sample of Example 8 was dried, and then a composition analysis was performed using SEM-EDX. The composition formula was found to be Ag ３５．２ Ge ５．５ S ４６．２ In １３．２ It was.

[0143] (Example 9) A sample (Ag—Ge—S nanoparticle dispersion solution) prepared in the same manner as in Comparative Example 1 was placed in a test tube in an amount of 4.0 nmol of particles, and the solvent was dried overnight in a vacuum desiccator. The number of particles was determined based on the molar absorption coefficient of the nanoparticles, 5.34 × 10 ６ The particle concentration was calculated from the absorbance measurement results of the nanoparticle dispersion solution using the HPLC method (L / (mol cm@365 nm) (L is liters)), and the nanoparticle dispersion solution equivalent to the required number of particles was taken.

[0144] After drying, 0.0270 mmol (=17.07 mg) of zinc stearate (MW=632.35) and 0.0270 mmol (=2.03 mg) of thioacetamide (MW=75.13) were added to the test tube as compound C2 containing multiple raw materials. A stirrer was placed in the test tube containing the core particles and compound C2 containing multiple raw materials, and the atmosphere was replaced with nitrogen. Then, 3 cm of dried oleylamine was injected into the test tube using a syringe. ３ was added to obtain a mixed solution M2.

[0145] The dried oleylamine was prepared in the same manner as in Example 1.

[0146] Then, the test tube was heated and stirred at a reaction temperature of 200° C. for 15 minutes using a hot stirrer.

[0147] After heating, the test tube was left to cool at room temperature for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate. The supernatant was then passed through a 0.20 μm membrane filter and recovered. No precipitate was formed. Next, 3 cm of methanol was added to the recovered supernatant. ３ The resulting precipitate was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３ The resulting precipitate was dried at room temperature for 10 minutes, and then 3 cm of chloroform (purity 99%, Kishida Chemical Co., Ltd.) was added as a non-polar solvent. ３ The particles were re-dispersed in the aqueous solution to prepare a sample (Ag—Ge—S / ZnS core-shell particle dispersion solution).

[0148] The sample (Ag-Ge-S / ZnS core-shell particle dispersion solution) was removed by 2 cm. ３ That is, 1.6 nmol of particles was dispensed into a test tube.

[0149] After drying in a desiccator under vacuum overnight, 0.0096 mmol (=0.72 mg) of thioacetamide (MW=75.13) was added to the test tube as a compound C1 containing a plurality of raw materials, and then 0.0096 mmol (=2.03 mg) of indium chloride (MW=211.18) was added in a glove box. The test tube was then charged with a stirrer containing core particles (core particles coated with a shell layer, i.e., core-shell particles) and a compound C1 containing a plurality of raw materials, and 3 cm of dried oleylamine was added using a syringe. ３ Mixture M1 was obtained.

[0150] The dried oleylamine was prepared in the same manner as in Example 1.

[0151] Then, the test tube containing the mixed solution M1 was heated and stirred with a hot stirrer at a reaction temperature of 110° C. for 15 minutes.

[0152] After heating, the test tube was left to cool at room temperature for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant from the precipitate. The supernatant was then passed through a 0.20 μm membrane filter and recovered. Next, 3 cm of methanol was added to the recovered supernatant. ３ The resulting precipitate was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３ The resulting precipitate was dried at room temperature for 30 minutes, and then 3 cm of chloroform (purity 99%, Kishida Chemical Co., Ltd.) was added as a non-polar solvent. ３ The resulting particles were re-dispersed in the aqueous solution to prepare a sample of Example 9 (Ag—Ge—S / (InS·ZnS) core-shell particle dispersion solution).

[0153] Then, as in Example 1, the solvent was dried off from the sample of Example 9, and then composition analysis was carried out using SEM-EDX. The composition formula was found to be Ag ２８．５ Ge ５．８ S ４７．１ In １０．５ Zn ８．１ It was.

[0154] (Comparative Example 2) A sample (Ag—Ge—S nanoparticle dispersion solution) prepared in the same manner as in Comparative Example 1 was placed in a test tube in an amount of 4.0 nmol of particles, and the solvent was dried overnight under reduced pressure. The number of particles was determined based on the molar absorption coefficient of the nanoparticles, 5.34 × 10 ６ The particle concentration was calculated from the absorbance measurement results of the nanoparticle dispersion solution using the HPLC method (L / (mol cm@365 nm) (L is liters)), and the nanoparticle dispersion solution equivalent to the required number of particles was taken.

[0155] After drying, 0.0270 mmol (=17.07 mg) of zinc stearate (MW=632.35) and 0.0270 mmol (=2.03 mg) of thioacetamide (MW=75.13) were added to the test tube as a shell (coating layer) precursor, i.e., a compound containing multiple raw materials. A stirrer was placed in the test tube containing the core particles and the compound containing multiple raw materials, and the atmosphere was replaced with nitrogen. Then, 3 cm of dried oleylamine was injected into the test tube using a syringe. ３ A mixed solution was obtained.

[0156] The dried oleylamine was prepared in the same manner as in Example 1.

[0157] The test tube containing the mixed solution was then heated and stirred with a hot stirrer at a reaction temperature of 200° C. for 15 minutes.

[0158] After heating, the test tube was left to cool at room temperature for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate. The supernatant was then passed through a 0.20 μm membrane filter and recovered. No precipitate was formed. Next, 3 cm of methanol was added to the recovered supernatant. ３ The resulting precipitate was centrifuged again at 4000 rpm for 5 minutes to separate the supernatant from the precipitate, and the supernatant was discarded. ３ The resulting precipitate was dried at room temperature for 10 minutes, and then 3 cm of chloroform (purity 99%, Kishida Chemical Co., Ltd.) was added as a non-polar solvent. ３ The resulting mixture was re-dispersed in the aqueous solution to prepare a sample of Comparative Example 2 (Ag—Ge—S / ZnS core-shell particle dispersion solution).

[0159] Then, as in Example 1, the solvent was dried off from the sample of Comparative Example 2, and then composition analysis was carried out using SEM-EDX. The composition formula was found to be Ag ２７．７ Ge ６．１ S ４３．７ Zn ２２．５ It was.

[0160] [Sample Evaluation] (Measurement of Particle Size) For each sample of Examples 1 to 9 and Comparative Examples 1 and 2, a transmission electron microscope (hereinafter referred to as "TEM") (Hitachi High-Technologies Corporation, H-7650) was used to take a TEM image, and the area of ​​100 randomly selected particles was measured. Next, the circle-equivalent diameter of each particle was calculated from the measured values ​​and the arithmetic mean was calculated, thereby determining the average particle size. In addition, the standard deviation σ of the average particle size of each sample was determined.

[0161] (Measurement of Absorption Spectrum, Emission Spectrum, and Emission Quantum Yield) The absorption spectrum of each of the samples of Examples 1 to 2 and 5 and Comparative Examples 1 and 2 was measured using a diode array spectrophotometer (8453a manufactured by Agilent Technologies).

[0162] Furthermore, for each of the samples of Examples 1 to 2 and 9 and Comparative Examples 1 and 2, the emission spectrum and emission quantum yield were measured at room temperature of 25° C. using an absolute luminescence quantum yield measurement apparatus (C9920-03 manufactured by Hamamatsu Photonics KK). Furthermore, for each of the samples of Examples 3 to 8, the emission quantum yield was measured at room temperature of 25° C. using the above-mentioned absolute luminescence quantum yield measurement apparatus.

[0163] (Measurement of XRD Diffraction Pattern) For the measurement of the XRD diffraction pattern, an X-ray diffractometer (SmartLab-3K manufactured by Rigaku Corporation) was used, and Cu Kα rays were used as the X-ray source.

[0164] (Evaluation of Measurement Results) FIG. 2 shows a TEM image of the sample of Example 1. As shown in FIG.

[0165] In Example 1, in which the coating layer contained an In component, nanoparticulate semiconductor particles were obtained in which the particle size variation was suppressed and which were uniformly or approximately uniformly dispersed, as shown in FIG.

[0166] 3 shows the absorption spectra of the samples of Examples 1 and 2 and Comparative Examples 1 and 2, with the horizontal axis representing wavelength (nm) and the vertical axis representing absorption coefficient (a.u.). Note that in these absorption spectra, the absorption coefficient on the vertical axis is normalized to the same standard so that the characteristics of each sample can be compared and evaluated.

[0167] As shown in Figure 3, absorption increases from a wavelength of around 800 nm toward shorter wavelengths in all samples. Although the absorption edge wavelength shifts toward shorter wavelengths due to the formation of core-shell particles, this is not a major change, and the results show that the coating layer is formed while the composition of the core particle is largely maintained. Regardless of the type of coating layer containing an In component or a coating layer containing both In and Zn components, no significant shift is observed from the absorption edge of the original core particle, indicating the formation of a core-shell structure.

[0168] That is, from this result and the result of the composition analysis described above, it was confirmed that the sample of Example 1 was a semiconductor nanoparticle with a core-shell structure in which a coating layer containing an In component and an S component as main components was formed on the surface of a core particle, and that the sample of Example 2 was a semiconductor nanoparticle with a core-shell structure in which a coating layer containing an In component, a Zn component, and an S component as main components was formed on the surface of a core particle.

[0169] Similarly, for each of the samples of Examples 3 to 4 and 6 to 9, it was confirmed from the results of the absorption spectrum and the above-mentioned composition analysis that they were semiconductor nanoparticles with a core-shell structure in which a coating layer containing an In component and an S component, or an In component, a Zn component and an S component as main components, was formed on the surface of the core particle.

[0170] 4 shows the emission spectra of each sample in Example 1 and Comparative Examples 1 and 2, with the horizontal axis representing wavelength (nm) and the vertical axis representing emission intensity (a.u.). The emission spectra were measured in a solution with an absorbance of 0.1 at the excitation light wavelength (365 nm) so that the number of absorbed photons by the sample was constant, and the emission intensity on the vertical axis can be evaluated while comparing the characteristics of each sample.

[0171] 4, it is clear that in Example 1 and Comparative Examples 1 and 2, light is emitted in the wavelength region of 1000 nm or less, which is at or on the longer wavelength side than the absorption edge wavelength. In particular, in Example 1, it was confirmed that the emission intensity has a mountain-shaped peak in the vicinity of 820 to 850 nm, which is near the absorption edge wavelength.

[0172] 4, Example 1, in which the coating layer contained an In component, exhibited a significant improvement in emission intensity compared to Comparative Example 1, which did not have a coating layer, and Comparative Example 2, in which the coating layer contained a Zn component instead of an In component. It is believed that in Example 1, the non-radiative defect levels on the nanoparticle surface were reduced by the coating layer containing an In component. It is also believed that the effect of reducing the defect levels was more effective than with a coating layer containing a Zn component.

[0173] Table 1 shows the composition formula, luminescence quantum yield, average particle size, standard deviation σ of the average particle size, reaction temperature and reaction time of the coating layer containing an In component, and reaction temperature and reaction time of the coating layer containing a Zn component for each sample in Examples 1 to 9 and Comparative Examples 1 and 2.

[0174]

[0175] As is clear from Table 1, in Examples 1 to 9 in which the coating layer contained an In component, a high luminescence quantum yield could be achieved.

[0176] 5 shows the emission spectra of the samples of Examples 1 and 2 and Comparative Example 1, with the horizontal axis representing wavelength (nm) and the vertical axis representing emission intensity (a.u.). The emission spectra were measured in a solution with an absorbance of 0.1 at the excitation light wavelength (365 nm) so that the number of absorbed photons by the sample was constant, and the emission intensity on the vertical axis can be evaluated while comparing the characteristics of each sample.

[0177] As shown in Figure 5, by forming a coating layer containing Zn in addition to In, higher luminescence intensity and fluorescence quantum yield can be achieved. ２ S ３ The energy gap of Ag-Ge-S compound semiconductor is about 2.1 eV, and Ag ８ GeS ６It is believed that because the band gap energy of the In and S components is wider than that of the In and S components (approximately 1.45 eV), it is possible to effectively block surface defects and effectively reduce non-radiative deactivation. Furthermore, by covering the coating layer containing the In and S components with a coating layer containing the Zn and S components (for example, the band gap energy of ZnS is approximately 3.7 eV), which has an even larger band gap energy, it is believed that the defect levels are further removed and the exciton confinement effect works effectively, resulting in even higher efficiency.

[0178] 6 shows the emission spectrum of the sample of Example 9, with the horizontal axis representing wavelength (nm) and the vertical axis representing emission intensity (a.u.). The emission spectrum was measured in a solution with an absorbance of 0.1 at the excitation light wavelength (365 nm) so that the number of absorbed photons by the sample was constant. The emission intensity on the vertical axis can be evaluated while comparing the characteristics of each sample.

[0179] As is clear from the emission spectrum of the sample of Example 2 shown in FIG. 5 and the emission spectrum of the sample of Example 9 shown in FIG. 6, the emission intensity can be significantly improved regardless of whether the coating layer containing the In component or the coating layer containing the Zn component is formed first.

[0180] FIG. 7 shows the XRD diffraction pattern of the sample of Example 5.

[0181] FIG. 7 shows AgInS ２ Since the peak positions match the data of Example 5, it is clear that the sample in Example 5 is AgInS ２ This suggests that a crystalline phase has been formed. ８ GeS ６ Since there is a peak (shoulder at 2θ = slightly less than 30°) that matches the reference data of Ag ８ GeS ６ and AgInS ２ However, from this result alone, it is not clear that the core particles are made of Ag. ８ GeS ６ (i.e., Ag-Ge-S nanoparticles), and the coating layer is AgInS ２ It cannot be determined that this is a phase.

[0182] 8 shows the absorption spectra of the samples of Examples 1 and 5 and Comparative Examples 1 and 2, with the horizontal axis representing wavelength (nm) and the vertical axis representing absorption coefficient (a.u.). Note that in these absorption spectra, the absorption coefficient on the vertical axis is normalized to the same standard so that the characteristics of each sample can be compared and evaluated.

[0183] From FIG. ２ 8 showing the optical absorption spectrum, the sample of Example 5 shows two-stage absorption characteristics: an absorption rise around 800 nm and a sharp absorption rise around 600 nm. The absorption around 800 nm is similar to that of Example 1 and Comparative Examples 1 and 2, and it can be determined that this is derived from the Ag-Ge-S nanoparticles (core particles). The absorption around 600 nm is due to the AgInS formed as a coating layer. ２ It can be determined that this is the origin.

[0184] From the above two analytical evaluation results, it was found that the coating layer of the sample of Example 5 was AgInS ２ It is clear that a coating layer is formed, and even when this coating layer is formed, the effect of realizing a high luminescence quantum yield can be obtained.

[0185] The present specification discloses the following:

[0186] <1> Semiconductor nanoparticles characterized by having a core-shell structure in which a coating layer containing an In component as a main component is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components.

[0187] <2> The semiconductor nanoparticles according to <1>, wherein the coating layer further contains a Zn component as a main component.

[0188] <3> The semiconductor nanoparticles according to <1> or <2>, wherein the coating layer further contains, as a main component, at least one element Z1 selected from the group of elements belonging to Group 16 of the periodic table.

[0189] <4> The semiconductor nanoparticles according to <3>, wherein the element Z1 includes at least one element selected from the group consisting of S and O.

[0190] <5> The semiconductor nanoparticles according to any one of <1> to <4>, wherein the coating layer further contains, as a main component, at least one element Z2 selected from the group of elements belonging to Group 11 of the periodic table.

[0191] <6> The semiconductor nanoparticles according to <5>, wherein the element Z2 includes Ag.

[0192] <7> The coating layer is made of AgInS ２ The semiconductor nanoparticles according to <6>, comprising:

[0193] <8> A method for producing semiconductor nanoparticles having a core-shell structure, in which a coating layer is formed on the surface of a core particle formed of a compound semiconductor containing an Ag component, a Ge component, and an S component as main components, the method comprising the steps of: preparing an Ag-Ge-S mixed solution in which an Ag compound, a Ge compound, and an S compound are dissolved in a solvent; and heating the Ag-Ge-S mixed solution to produce a core particle made of a compound semiconductor; and adding the core particle made of the compound semiconductor and a plurality of raw material-containing compounds C1 including an In compound to a solvent to prepare a mixed solution M1; and heating the mixed solution M1 to 70°C or higher to cause a reaction.

[0194] <9> The method for producing semiconductor nanoparticles according to <8>, further comprising the steps of: adding the core particles made of the compound semiconductor and a plurality of raw material-containing compounds C2 including a Zn compound to a solvent to prepare a mixed solution M2; and heating the mixed solution M2 to cause a reaction.

[0195] <10> The method for producing semiconductor nanoparticles according to <9>, wherein the mixed solution M2 is heated to a reaction temperature of 50° C. or higher and 200° C. or lower.

[0196] <11> A light emitter comprising the semiconductor nanoparticles according to any one of <1> to <7>.

[0197] 10 semiconductor nanoparticle 11 core particle 12 coating layer

Claims

1. Semiconductor nanoparticles characterized by a core-shell structure in which a coating layer containing In as a main component is formed on the surface of a core particle formed from a compound semiconductor containing Ag, Ge, and S as main components.

2. The semiconductor nanoparticles according to claim 1, wherein the coating layer further contains Zn as a main component.

3. The semiconductor nanoparticles according to claim 1 or 2, characterized in that the coating layer further contains, as a main component, at least one element Z1 selected from the group of elements belonging to Group 16 of the periodic table.

4. The semiconductor nanoparticles according to claim 3, wherein the element Z1 includes at least one element selected from the group consisting of S and O.

5. The semiconductor nanoparticles described in any one of claims 1 to 4, characterized in that the coating layer further contains, as a main component, at least one element Z2 selected from the group of elements belonging to Group 11 of the periodic table.

6. The semiconductor nanoparticles according to claim 5, wherein the element Z2 includes Ag.

7. The coating layer is AgInS ２ The semiconductor nanoparticles according to claim 6, comprising:

8. A method for producing semiconductor nanoparticles having a core-shell structure in which a coating layer is formed on the surface of core particles formed of a compound semiconductor primarily composed of Ag, Ge, and S components, the method comprising the steps of: preparing an Ag-Ge-S mixed solution in which Ag compounds, Ge compounds, and S compounds are dissolved in a solvent; and heating the Ag-Ge-S mixed solution to produce core particles made of a compound semiconductor; and adding the core particles made of the compound semiconductor and a plurality of raw material-containing compounds C1 including an In compound to a solvent to prepare a mixed solution M1; and heating the mixed solution M1 to 70°C or higher to cause a reaction.

9. The method for producing semiconductor nanoparticles described in claim 8, further comprising the step of adding core particles made of the compound semiconductor and a plurality of raw material-containing compounds C2 including a Zn compound to a solvent to prepare a mixed solution M2, and heating the mixed solution M2 to cause a reaction.

10. The method for producing semiconductor nanoparticles according to claim 9, wherein the mixed solution M2 is heated to a reaction temperature of 50°C or higher and 200°C or lower.

11. A light-emitting body comprising the semiconductor nanoparticles according to any one of claims 1 to 7.

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