SEMICONDUCTOR NANOPARTICLES COMPRISING MULTICOMPONENT AgAu CHALCOGEN COMPOUND

Abstract

The present invention relates to semiconductor nanoparticles comprising a multicomponent AgAu chalcogen compound containing Ag, Au, a chalcogen element, a metal M1, and a metal M2. The chalcogen element of the AgAu chalcogen compound is at least one of S, Se, and Te, the metal M1 is at least one of In, Al, Ga, Tl, Cd, Hg, and Cu, and the metal M2 is Zn. The metal M1 contributes to improvement of optical semiconductor characteristics of the AgAu chalcogen compound, and Zn, which is the metal M2, has an effect of improving durability to hydrophilization treatment. The semiconductor nanoparticles according to the present invention may each have a double-shell structure having the AgAu chalcogen compound serving as a core, and first and second shells containing the metal M1 and the metal M2, respectively. These semiconductor nanoparticles have suitable optical semiconductor characteristics and durability, and are suppressed in damage and characteristic change during the hydrophilization treatment.

Description

Semiconductor nanoparticles made of AgAu chalcogenide multicomponent

[0001] The present invention relates to semiconductor nanoparticles made of a transition metal chalcogen compound (AgAu chalcogen compound) using Ag and Au as transition metals. More specifically, the present invention relates to semiconductor nanoparticles made of an AgAu chalcogen compound with two metal elements added thereto, which exhibit suppressed deterioration in optical semiconductor properties even after replacement with a protective agent for hydrophilization.

[0002] When semiconductors are made into nanoscale particles, they exhibit a quantum confinement effect and exhibit a band gap that corresponds to their particle size. Therefore, by controlling the composition and particle size of semiconductor nanoparticles to adjust the band gap, it is possible to arbitrarily set the emission wavelength and absorption wavelength. Semiconductor nanoparticles that utilize this property are also called quantum dots (QDs) and are expected to be used in various technical fields. For example, semiconductor nanoparticles are being investigated for their response to light-emitting elements and fluorescent substances used in display devices and marker substances for detecting biological substances. As described above, in addition to the ability to freely control the emission wavelength of semiconductor nanoparticles by controlling their particle size, the emission peak width of semiconductor nanoparticles is sufficiently narrower than that of organic dyes and they are more stable than organic dyes under excitation light irradiation. This suggests their potential application in light-emitting devices, etc.

[0003] Semiconductor nanoparticles are also expected to be used in photoelectric conversion elements and light-receiving elements installed in solar cells, optical sensors, etc. In addition to being able to control the absorption wavelength depending on the particle size, they also have the properties of high quantum efficiency and a high absorption coefficient. These properties mean that semiconductor nanoparticles can contribute to the miniaturization and thinning of semiconductor devices.

[0004] Known specific examples of semiconductor nanoparticles include transition metal chalcogen compounds, which are compounds of transition metals such as Cd, Zn, Cu, Au, Ag, and Pt with chalcogen elements such as S and Se (for example, Patent Document 1 provides numerous examples of quantum dots made of transition metal chalcogen compounds). The present applicant has previously disclosed several studies on semiconductor nanoparticles made of transition metal chalcogen compounds, and has reported the usefulness of chalcogen compounds using Ag and Au as the transition metal (Patent Documents 2 and 3). Furthermore, the present applicant has demonstrated that semiconductor nanoparticles made of AgAu chalcogen multicomponent compounds, in which a metal such as In is added to an AgAu chalcogen compound, have optical absorption characteristics with an absorption edge in the long wavelength region of 900 nm or more and exhibit excellent luminescence (Patent Document 2).

[0005] JP 2023-004874 A Patent No. 7269591 Patent No. 7521746

[0006] When using fine particle functional materials such as semiconductor nanoparticles for various applications, dispersions (inks) in which semiconductor nanoparticles are dispersed in an appropriate dispersion medium are often used. This is to ensure that the semiconductor nanoparticles are uniformly adsorbed and bonded to the substrate or carrier in the application. Furthermore, to prevent the semiconductor nanoparticles from aggregating in the dispersion and maintain their dispersed state, organic substances known as protective agents, surfactants, etc. are typically bonded to the semiconductor nanoparticles.

[0007] The protective agent is applied from the synthesis stage of semiconductor nanoparticles, is introduced into the reaction system together with the raw materials (precursors), and bonds to the semiconductor nanoparticles at the moment of synthesis, imparting dispersibility. The protective agent introduced at this synthesis stage does not easily separate from the semiconductor nanoparticles, and remains bonded to the semiconductor nanoparticles unless volatilized or decomposed by the application of energy such as heating. Therefore, the above-mentioned dispersion of semiconductor nanoparticles usually contains the protective agent at the synthesis stage.

[0008] Incidentally, when considering the use in the various applications described above, aqueous dispersion media are sometimes preferred as dispersion media for semiconductor nanoparticle dispersions. This is because substrates and boards for sensors and the like are often cleaned by plasma treatment or the like, making their surfaces hydrophilic. Furthermore, in the manufacture of devices intended for use on the human body, such as biodevices, aqueous dispersion media are preferred to ensure biosafety. Furthermore, when considering use at device manufacturing sites, aqueous dispersion media and solvents are preferred due to issues such as work safety and wastewater treatment.

[0009] Because the dispersibility of semiconductor nanoparticles is affected by the polarity of the protective agent to which they are bonded, the use of a hydrophilic protective agent is preferred for dispersion in an aqueous dispersion medium. Specifically, organic substances with short carbon chains are preferred as hydrophilic protective agents. However, organic substances with long carbon chains are often used as protective agents in the synthesis stage of semiconductor nanoparticles to enhance their protective effect. Because long-carbon-chain protective agents tend to be hydrophobic, the semiconductor nanoparticles after synthesis are dispersed in a low-polarity organic solvent, making it difficult to disperse them directly in an aqueous dispersion medium. Therefore, a treatment to impart hydrophilicity to the synthesized semiconductor nanoparticles is required. One hydrophilization treatment for imparting hydrophilicity involves contacting a hydrophilic protective agent (a short-carbon-chain organic substance) with semiconductor nanoparticles to which a protective agent has been bonded during synthesis and replacing the protective agent with the hydrophilic protective agent through a ligand exchange reaction.

[0010] However, conventional semiconductor nanoparticles may be damaged or deteriorated during the hydrophilization treatment. Damage to semiconductor nanoparticles refers to the dissolution of part or all of the particles into the solvent during the ligand exchange reaction. Even in semiconductor nanoparticles that do not exhibit the above-mentioned dissolution and retain their original shape after ligand exchange, degradation of optical properties may occur, such as the loss of luminescence that was present before the hydrophilization treatment. Semiconductor nanoparticles that suffer from such damage or deterioration may be problematic in practical use, even if their inherent properties are excellent.

[0011] The present invention has been made against the background described above, and provides semiconductor nanoparticles of a predetermined configuration that have suitable optical semiconductor properties, and that are less likely to be damaged or have their properties changed even when subjected to the above-mentioned hydrophilization treatment.

[0012] In order to solve the above-mentioned problems, the present inventors conducted a more detailed study on semiconductor nanoparticles made of the aforementioned AgAu chalcogen multicomponent compound (Patent Document 2), in which Ag and Au are transition metals. In these semiconductor nanoparticles made of AgAu chalcogen multicomponent compounds, the optical semiconductor properties are improved by adding a metal element such as In to the AgAu chalcogen compound (AgAuS). The present inventors focused on the effect of Zn, among the metal elements added to the AgAu chalcogen compound in this prior art. According to the study of the present invention, In is particularly effective in improving the properties of the AgAu chalcogen compound (AgAuS), while Zn is not as effective as In. Furthermore, semiconductor nanoparticles made of AgAu chalcogen multicomponent compounds to which metal elements such as Zn and In are added alone also suffer from the above-mentioned technical problems, and it has been confirmed that replacing the protective agent with a hydrophilic protective agent results in a loss of the original favorable optical semiconductor properties. However, when Zn is added to an AgAu chalcogen compound together with other metals such as In, the semiconductor nanoparticles acquire resistance to the hydrophilization treatment and can maintain their properties before hydrophilization. Although the reason why Zn has this effect is not clear, the inventors of the present invention came up with the idea that semiconductor nanoparticles obtained by appropriately adding Zn to an AgAu chalcogen compound can remove the barrier to hydrophilization.

[0013] That is, the present invention, which solves the above-mentioned problems, provides semiconductor nanoparticles composed of a compound containing Ag, Au, a chalcogen element, a metal M1, and a metal M2, wherein the chalcogen element is at least one of S, Se, and Te, the metal M1 is at least one of In, Al, Ga, Tl, Cd, Hg, and Cu, and the metal M2 is Zn, and the compound is a semiconductor nanoparticle in which the total content of Ag, Au, the chalcogen element, the metal M1, and the metal M2 is 95 mass% or more.

[0014] The structure of semiconductor nanoparticles made of an AgAu chalcogen compound according to the present invention and a method for producing the same will be described below. For convenience, in this specification, a ternary chalcogen compound made of Ag, Au, and a chalcogen element may be referred to as an "AgAu chalcogen compound." Furthermore, a quaternary or higher compound obtained by adding metal M1 or metal M1 and metal M2 to an "AgAu chalcogen compound" may be referred to as an "AgAu chalcogen multi-component compound."

[0015] A. Structure of the Semiconductor Nanoparticles According to the Present Invention A-1. Constituent Elements of the Semiconductor Nanoparticles As described above, the semiconductor nanoparticles according to the present invention are nanoparticles made of a multi-component AgAu chalcogen compound in which a metal M1 and Zn, which is a metal M2, are added to an AgAu chalcogen compound. Ag and Au are essential elements as transition metal components that constitute the compound.

[0016] Metal M1 is an essential additive element for improving the optical semiconductor properties of the AgAu chalcogen compound. Metal M1 is composed of at least one of In, Al, Ga, Tl, Cd, Hg, and Cu. The addition of metal M1 can achieve improved properties, such as shifting the absorption edge wavelength to a longer wavelength region and improving the luminescence quantum efficiency in the luminescence phenomenon, compared to semiconductor nanoparticles made of the AgAu chalcogen compound before addition. The reason why metal M1 has such effects is not clear, but the inventors believe that these metal elements relieve surface defects and lattice distortions contained in the crystals of the AgAu chalcogen compound. In is particularly preferred as metal M1, as In is particularly useful for improving the optical semiconductor properties of the AgAu chalcogen compound.

[0017] In the present invention, the metal M2 added to the AgAu chalcogen compound is Zn. The metal M2 is an additive element that imparts durability to the semiconductor nanoparticles against hydrophilization treatment. By further adding Zn to the semiconductor nanoparticles made of the AgAu chalcogen compound, even if a protective agent replacement treatment is performed, the original state and characteristics of the semiconductor nanoparticles can be maintained without causing deterioration of the optical semiconductor characteristics due to elution or aggregation of the semiconductor nanoparticles.

[0018] The total content of metal M1 and metal M2, which are additive elements in the AgAu chalcogen compound constituting the semiconductor nanoparticles according to the present invention, is preferably 1 atomic % or more and 50 atomic % or less. If the content is less than 1 atomic %, there is essentially no difference from the AgAu chalcogen compound. Furthermore, if the content exceeds 50 atomic %, the effect of improving characteristics such as quantum efficiency is significantly reduced. The content of these additive elements is more preferably 1 atomic % or more and 20 atomic % or less. Furthermore, the ratio M1 / M2, which is the ratio of the content of metal M1 to the content of metal M2 in the AgAu chalcogen compound, is preferably 0.5 or more and 1.5 or less.

[0019] Regarding the contents of Ag and Au, which are essential constituent elements of the AgAu chalcogen compound of the present invention, the properties vary depending on the abundance ratio of Ag and Au in the compound. In the present invention, the ratio (x / (x+y)) of the number of Ag atoms to the sum of the number of Ag atoms (x) and the number of Au atoms (y) in the compound is preferably 0.50 or more and 0.90 or less. The lower limit of the ratio of the number of Ag atoms is more preferably 0.75 or more, and even more preferably 0.8 or more. The upper limit of the ratio of the number of Ag atoms is more preferably 0.85. Within these composition ranges, the effect of increasing luminescence quantum efficiency, etc. becomes clear.

[0020] Furthermore, the chalcogen elements of the AgAu chalcogen compound are S, Se, and Te. The optical semiconductor properties of transition metal chalcogen compounds may be correlated with the mass (atomic weight) of the chalcogen element. It is presumed that as the mass of the chalcogen element of a transition metal chalcogen compound increases, the orbital energy difference between the transition metal element and the chalcogen element decreases, thereby shifting the photoresponse to the longer wavelength side. However, in addition to the absorption wavelength, the optical semiconductor properties of semiconductor nanoparticles should also be evaluated, including the presence or absence of light emission, the emission spectrum wavelength, and the luminescence quantum efficiency, and these are not necessarily affected by the mass of the chalcogen element. Taking these factors into consideration, the chalcogen elements of the AgAu chalcogen compound of the present invention are S, Se, and Te.

[0021] The chalcogen element is contained in the AgAu chalcogen compound so as to compensate for the charge of the metal element (positive charge) of the AgAu chalcogen compound. The metal here refers to Ag, Au, In, and Zn. The content of the chalcogen element in the AgAu chalcogen compound varies depending on the valence and content of the metal element. The content of the chalcogen element in the AgAu chalcogen compound of the present invention is preferably 30 atomic % or more and 60 atomic % or less. The content of the chalcogen element is more preferably 35 atomic % or more and 45 atomic % or less.

[0022] The semiconductor nanoparticles according to the present invention are composed of an AgAu chalcogen multicomponent compound having Ag, Au, a chalcogen element, a metal M1, and a metal M2 as essential constituent elements. The AgAu chalcogen compound has a total content of Ag, Au, a chalcogen element, a metal M1, and a metal M2 of 95% by mass or more. Possible elements that may be contained other than the above elements include Ge, Si, Sn, Pb, O, etc., and these elements are acceptable if they are present in an amount of less than 5% by mass. However, the compound preferably has a total content of Ag, Au, a chalcogen element, and a metal M of 99% by mass or more, more preferably 99.9% by mass or more. The compositional value of the compound here refers to the value of the AgAu chalcogen multicomponent compound constituting the semiconductor nanoparticles, and does not include the components of the protective agent described below.

[0023] A-2. Structure of Semiconductor Nanoparticles In the method for producing semiconductor nanoparticles described in detail later, semiconductor nanoparticles made of a ternary AgAu chalcogen compound are first synthesized, and then metal M1 and Zn are added sequentially. Considering this synthesis process, it is highly likely that the structure of the semiconductor nanoparticles according to the present invention is such that Zn, which is added last, is essentially present on the outermost surface. It is also presumed that metal M1 is present on the surface of the AgAu chalcogen compound.

[0024] Considering the distribution of the metal M1 and Zn as described above, the compound constituting the semiconductor nanoparticles of the present invention can have a so-called core-shell structure with an AgAu chalcogen compound at the center (core). Specifically, the following two types of structures can be mentioned.

[0025] First, there is mentioned a core / first shell / second shell core-shell structure (core / double shell structure) consisting of a core compound containing Ag, Au, and a chalcogen element, a first shell compound consisting of a metal M1 or essentially containing the metal M1 and containing at least one of Ag, Au, and a chalcogen element, and a second shell compound consisting of a metal M2 or essentially containing the metal M2 and containing at least one of Ag, Au, a chalcogen element, and a metal M1. In this case, in the AgAu chalcogen multi-component compound, the first shell compound covers at least a portion of the surface of the core compound, and the second shell compound covers at least a portion of the surface of the core compound and / or at least a portion of the surface of the first shell compound.

[0026] In this configuration, the first and second shells may contain Ag, Au, and chalcogen elements because interdiffusion may occur between the core AgAu chalcogen compound and the first and second shell layers during the semiconductor nanoparticle formation process or in the subsequent thermal atmosphere.

[0027] In addition, the structure of the semiconductor nanoparticles of the present invention can take a form in which the core compound is coated with a double shell compound as described above, or a form in which the core compound is coated with a single shell compound. In this case, the semiconductor nanoparticles are composed of a core compound containing Ag, Au, and a chalcogen element, and a third shell compound consisting of metal M1 and metal M2, or essentially containing metal M1 and metal M2 and at least one of Ag, Au, and a chalcogen element. The third shell compound then coats at least a portion of the surface of the core compound. This form is formed by interdiffusion between the first and second shell compounds, resulting in the formation of a single shell compound (third shell compound) containing components of both shell compounds (metal M1, metal M2, etc.).

[0028] The semiconductor nanoparticles according to the present invention may have a core-shell structure as described above, but the shell compound may have different configurations. The shell compound configuration may vary depending on the synthesis conditions of the semiconductor nanoparticles, the thermal history after synthesis, and changes over time. However, in any configuration, the outermost layer of the semiconductor nanoparticles according to the present invention contains Zn, which is the metal M2. This is thought to contribute to the development of durability against hydrophilization treatment.

[0029] The element distribution (element arrangement) in the AgAu chalcogen compound constituting the present invention may be regular or irregular. For example, when the semiconductor nanoparticles have the above-mentioned core-shell structure, the AgAu chalcogen compound as the core is not necessarily composed of a single phase, but may be composed of a mixed phase. The compound phase may have a stoichiometric composition or may not have a stoichiometric composition. For example, when the chalcogen element is S, the AgAuS compound present in the semiconductor nanoparticles of the present invention is Ag １ Au ７ S ４ , AgAu ３ S ２ , Ag ３ Au ５ S ４ , AgAuS, Ag ５ Au ３ S ４ , Ag ３ AuS ２ , Ag ７ AuS ４ The composition may be a stoichiometric composition such as above, or may be a composition that deviates from this.

[0030] Furthermore, the constituent elements of the above-mentioned shell compounds (first, second, and third shell compounds) are not necessarily distributed completely evenly, and the shell compounds should be identified based on the presence or absence of the constituent elements (metal M1, metal M2, Ag, Au, and chalcogen elements) defined above.

[0031] Structural analysis of the semiconductor nanoparticles according to the present invention can be performed using a transmission electron microscope (TEM). Furthermore, a scanning transmission electron microscope (Scanning TEM) can be suitably used. Furthermore, a high-angle annular dark-field scanning transmission microscope (HAADF-STEM) can obtain a scattering image that reflects the compositional information of the nanoparticles. In combination with an energy-dispersive X-ray spectrometer (EDX), the distribution of Ag, Au, chalcogen elements, metal M1, and metal M2, as well as the overall composition of the nanoparticles, can be ascertained.

[0032] The semiconductor nanoparticles according to the present invention preferably have an average particle size of 2 nm or more and 20 nm or less. The particle size of the semiconductor nanoparticles is related to the band gap adjustment effect due to the quantum confinement effect. In order to exhibit favorable light emission and light absorption properties due to band gap adjustment, it is preferable to set the average particle size as described above. The average particle size of the semiconductor nanoparticles can be obtained by observing a plurality of particles (preferably 100 or more) using an electron microscope such as a TEM, measuring the particle size of each particle, and calculating the particle number average.

[0033] A-3. Protective Agent for Semiconductor Nanoparticles The semiconductor nanoparticles according to the present invention can be dispersed in a dispersion medium by bonding with an appropriate protective agent. As described above, a suitable dispersion medium is selected for the semiconductor nanoparticles depending on the polarity of the protective agent.

[0034] Examples of protective agents for semiconductor nanoparticles of the present invention include alkylamines having an alkyl chain carbon number of 4 to 20 but not more than 20, alkenylamines having an alkenyl chain carbon number of 4 to 20 but not more than 20, alkylcarboxylic acids having an alkyl chain carbon number of 3 to 20 but not more than 20, alkenylcarboxylic acids having an alkenyl chain carbon number of 3 to 20 but not more than 20, alkanethiols having an alkyl chain carbon number of 4 to 20 but not more than 20, trialkylphosphines having an alkyl chain carbon number of 4 to 20 but not more than 20, trialkylphosphine oxides having an alkyl chain carbon number of 4 to 20 but not more than 20, triphenylphosphine, and triphenylphosphine oxide. These protective agents are introduced into the synthesis reaction system together with precursors of AgAu chalcogen compounds (Ag precursors, Au precursors, chalcogen compounds, etc.) during the synthesis of semiconductor nanoparticles, and bond to the particle surfaces simultaneously with the synthesis of semiconductor nanoparticles. These protective agents have relatively strong bonding strength with semiconductor nanoparticles and high protective ability, and can maintain the bonded state with semiconductor nanoparticles after synthesis while ensuring a dispersed state in the dispersion medium. These protective agents are effective for dispersing semiconductor nanoparticles in low-polarity solvents (hydrophobic solvents). As the low polarity solvent, chloroform, toluene, cyclohexane, hexane, etc. can be used.

[0035] As described above, the protective agent bonded to the synthesized semiconductor nanoparticles can be replaced with a hydrophilic protective agent by ligand exchange. Bonding with a hydrophilic protective agent allows the semiconductor nanoparticles to acquire dispersibility in aqueous solvents. Examples of such hydrophilic protective agents include thiols having 3 or fewer carbon atoms, sulfides having 3 or fewer carbon atoms, disulfides having 3 or fewer carbon atoms, thioesters having 3 or fewer carbon atoms, and thioketones having 3 or fewer carbon atoms. Specific examples of such protective agents include 3-mercaptopropionic acid (MPA), 2-mercaptoethanol, 2-mercaptoethanesulfonic acid, and 2-dimethylaminoethanethiol. Semiconductor nanoparticles bonded with such hydrophilic protective agents are expected to be used in devices applied to the human body, such as biosensors and markers. Furthermore, the short carbon chains of the protective agent reduce interparticle distances and increase density, potentially improving electrical conductivity, enabling applications in devices other than those for biological applications. Examples of dispersion media for semiconductor nanoparticles bonded with a hydrophilic protective agent include water, alcohol, and ionic liquids.

[0036] A-4. Optical Semiconductor Properties of Semiconductor Nanoparticles As mentioned at the beginning, the band gap of semiconductor nanoparticles is adjusted by the quantum confinement effect depending on the particle size, and the light absorption characteristics change. The semiconductor nanoparticles according to the present invention preferably have an absorption edge wavelength of 600 nm or more on the long-wavelength side of the absorption spectrum. This allows the semiconductor nanoparticles to have absorption and responsiveness to light in the visible to near-infrared region. In a more preferred embodiment, the present invention can provide semiconductor nanoparticles having an absorption edge wavelength of 700 nm or more on the long-wavelength side of the absorption spectrum.

[0037] Furthermore, the semiconductor nanoparticles according to the present invention can also exhibit a favorable luminescence phenomenon. In this case, the emission spectrum exhibits an emission peak wavelength in the wavelength region of 700 nm or more. In a more preferred embodiment, the semiconductor nanoparticles according to the present invention can exhibit an emission peak wavelength in the long wavelength region of 780 nm or more.

[0038] Furthermore, the semiconductor nanoparticles of the present invention are less susceptible to the effects of the ligand exchange reaction, and exhibit good durability in terms of maintaining their optical semiconductor properties. Even after undergoing hydrophilization treatment through ligand exchange, the semiconductor nanoparticles can maintain the above-mentioned light absorption and light emission properties.

[0039] A-5. Use of Semiconductor Nanoparticles By coating and supporting the semiconductor nanoparticles according to the present invention on an appropriate substrate or carrier, they can be applied to the various uses mentioned above, such as light-emitting devices. There are no particular limitations on the structure, shape, or dimensions of the substrate or carrier. Examples of substrates in the form of a plate or foil or film include glass, quartz, silicon, ceramics, or metal. In addition, examples of granular or powdered carriers include ZnO, TiO ２ , W.O. ３ , SnO ２ , In ２ O ３ , Al ２ O ３ The semiconductor nanoparticles may be supported on the inorganic oxide support and then fixed to a substrate.

[0040] When semiconductor nanoparticles are applied to and supported on a substrate or carrier, a solution, slurry, or ink is used in which the semiconductor nanoparticles are dispersed in a dispersion medium with the protective agent bonded thereto. In the present invention, a hydrophilic or hydrophobic protective agent can be selected as desired, taking into consideration the polarity of the dispersion medium. Specific protective agents and dispersion media are as described above. Furthermore, the present invention is applicable to both hydrophilic and hydrophobic substrates.

[0041] As a method for applying a solution of semiconductor nanoparticles, dipping or spin coating can be used, and as a method for supporting the semiconductor nanoparticles, various methods such as dropping, impregnation or adsorption can be used, regardless of the types of protective agent, dispersion medium and substrate.

[0042] B. Method for Producing Semiconductor Nanoparticles According to the Present Invention Next, a method for producing semiconductor nanoparticles according to the present invention will be described. The semiconductor nanoparticles of the present invention include a step of producing nanoparticles made of an AgAu chalcogen compound, a step of adding a metal M1 to the AgAu chalcogen compound, and a step of adding a metal M2. Below, a method for producing an AgAu chalcogen compound (synthesis method) and a step of adding a metal M1 and a metal M2 to the AgAu chalcogen compound will be described.

[0043] B-1. Manufacturing Process of AgAu Chalcogen Compound Nanoparticles Nanoparticles made of AgAu chalcogen compounds can be manufactured by mixing an Ag precursor, an Au precursor, and, if necessary, a chalcogen compound in a reaction solvent, and heating the reaction system formed from these at a temperature of 100°C or higher and 200°C or lower.

[0044] The Ag precursor and Au precursor, which are raw materials for the AgAu chalcogen compound, are preferably Ag salts or Ag complexes, and Au salts or Au complexes, respectively. The Ag precursor and Au precursor are preferably salts or complexes containing monovalent Ag or monovalent Au. However, for the Au precursor, a precursor containing trivalent Au can be used. This is because, during the synthesis of semiconductor nanoparticles, trivalent Au is reduced to monovalent Au by a solvent or coexisting chalcogen elements. Furthermore, it is preferable that at least one of the Ag precursor and Au precursor be a complex having a ligand containing a chalcogen element. In this case, the chalcogen element contained in the ligand of the Ag complex and / or Au complex can be used as a source of the chalcogen element for the AgAu chalcogen compound, thereby synthesizing the compound.

[0045] Suitable Ag precursors include silver acetate (Ag(OAc)), silver nitrate, silver carbonate, silver oxide, silver oxalate, silver chloride, silver iodide, silver(I) cyanide salts, etc. Suitable Au precursors include Au resinate (C １０ H １８ Au ２ S ２ : CAS68990-27-2), chloro(dimethyl sulfide) gold(I) ((CH ３ ) ２SAuCl), gold iodide (I), gold sulfite (I), chloroauric acid (III), gold acetate (III), gold cyanide (I), gold cyanide (III), 1,10-phenanthroline gold (III), and the like.

[0046] When a chalcogen compound is used, the sulfur compound when the chalcogen element is S may be powdered elemental sulfur, or compounds such as thiourea, alkylthiourea, thioacetamide, or alkanethiol, or compounds such as β-dithiones, dithiols, xanthogenates, or diethyldithiocarbamates. When the chalcogen element is Se, the selenium compound may be powdered elemental selenium, or selenourea (Se═C(NH ２ ) ２ ), selenocysteine, trioctylphosphine selenide, triphenylphosphine selenide, diphenyl diselenide, dibenzyl diselenide, etc. When the chalcogen element is Te, tellurium compounds such as tellurium oxide (TeO ２ ), telluric acid (Te(OH) ６ ), sodium tellurite (Na ２ TeO ３ The chalcogen compound may be added to the reaction system even if it is an Ag complex or an Au complex having a ligand containing a chalcogen element.

[0047] The composition of the synthesized AgAu chalcogen compound can be adjusted by the mixing ratio (charged atomic ratio) of the Ag precursor and the Au precursor. To obtain a suitable AgAu chalcogen compound, the atomic ratio of the metal atoms contained in the charged amounts of the Ag precursor and the Au precursor (Ag:Au) is preferably set to between 0.78:0.22 and 0.14:0.86, where a:b is the atomic ratio of the metal atoms contained therein. Furthermore, the amount of chalcogen element in the reaction system is preferably set to an atomic ratio of 0.25 to 0.60 relative to the total number of Ag and Au atoms in the reaction system. However, even if there is an excess of chalcogen element in the reaction system, the effect on the composition of the AgAu chalcogen compound is minimal.

[0048] The reaction system for synthesizing semiconductor nanoparticles can be produced without a solvent, or a solvent may be used. When a solvent is used, octadecene, tetradecane, oleic acid, oleylamine, dodecanethiol, or a mixture thereof can be used.

[0049] As described above, it is preferable to use a protective agent when synthesizing AgAu chalcogen compound nanoparticles. The protective agent in this case is preferably an organic compound having 4 or more carbon atoms as described above.

[0050] The heating temperature (reaction temperature) of the reaction system composed of the Ag precursor, the Au precursor, the chalcogen compound, and the protective agent is preferably 50°C or higher and 200°C or lower. At temperatures below 50°C, the synthesis of the AgAu chalcogen compound is difficult to proceed. On the other hand, at temperatures above 200°C, there is a risk that Au alone may form nanoparticles, preventing the production of a compound with the desired composition. The average particle size of the semiconductor nanoparticles increases with increasing reaction temperature, but rarely exceeds the preferred average particle size within the above temperature range. A more preferred reaction temperature is 100°C or higher and 165°C or lower. The heating time (reaction time) can be adjusted depending on the amount of raw materials charged, but is preferably 1 minute or higher and 60 minutes or lower. It is preferable to stir the reaction system during the synthesis reaction of the semiconductor nanoparticles.

[0051] After the synthesis reaction of the AgAu chalcogen compound nanoparticles is completed, the reaction system is cooled as necessary, and the AgAu chalcogen compound nanoparticles are recovered. At this time, the nanoparticles may be precipitated by adding alcohol (ethanol, methanol, etc.) as a poor solvent, or the semiconductor nanoparticles may be precipitated and recovered by centrifugation or the like, and the particles may be further washed with alcohol (ethanol, methanol, etc.) and then uniformly dispersed in a good solvent such as chloroform.

[0052] B-2. Addition of Metal M1 to AgAu Chalcogen Compound Nanoparticles The addition of metal M1 to AgAu chalcogen compound nanoparticles can be performed without a solvent, but is preferably performed in a solvent. The solvent can be the same as the AgAu chalcogen compound reaction system described above. The reaction system containing the AgAu chalcogen compound nanoparticles produced above may be used as is, or the nanoparticles may be recovered by a known separation means and then redispersed in a solvent to form a reaction system.

[0053] In the process of adding the metal M1 to the AgAu chalcogen compound nanoparticles, a compound of the metal M1 is added as a metal M1 precursor to the reaction system, mixed, and heated. The metal M1 compound serving as the metal M1 precursor is preferably a chalcogen compound of the metal M1, including chlorides, sulfides, nitrates, acetates, sulfates, sulfamates, and the like. Examples of suitable compounds include indium chloride, indium sulfide, indium acetate, indium diethyldithiocarbamate, indium selenide, and indium telluride. The content of the metal M1 in the semiconductor nanoparticles of the present invention is adjusted by the amount of the metal M1 precursor added. The metal M1 compound is preferably added in solution form. The intended amount of solution may be added in its entirety or by adding it dropwise in small amounts. A chalcogen compound may also be added to the reaction system when the metal M1 precursor is added. The chalcogen compound added in this case may be the same as the compound serving as the precursor of the chalcogen element described above.

[0054] The heating temperature for adding the metal M1 to the AgAu chalcogen compound nanoparticles is preferably 80°C or higher and 200°C or lower. At temperatures below 80°C, it is difficult to obtain a stable bond between the AgAu chalcogen compound nanoparticles and the metal M1. On the other hand, at temperatures above 200°C, decomposition of the AgAu chalcogen compound may occur. A more suitable reaction temperature is 100°C or higher and 150°C or lower. The heating time (reaction time) can be adjusted depending on the amount of each component added to the reaction system, and is preferably 5 minutes or higher and 60 minutes or lower. It is preferable to stir the reaction system. The above reaction process allows the production of semiconductor nanoparticles made of an AgAu chalcogen compound in which the metal M1 is added to the AgAu chalcogen compound.

[0055] B-3. ​​Addition of Metal M2 to AgAu Chalcogen Compound Nanoparticles By adding Zn as metal M2 to the AgAu chalcogen compound nanoparticles to which metal M1 has been added by the above process, semiconductor nanoparticles made of an AgAu chalcogen compound with a core / double shell structure are formed. The addition of metal M2 to the AgAu chalcogen compound nanoparticles is also preferably carried out in a solvent. Metal M2 can be added to the same reaction system following the addition of metal M1. Alternatively, the semiconductor nanoparticles to which metal M1 has been added may be temporarily recovered and redispersed in a solvent before metal M2 is added.

[0056] The process of adding metal M2 to AgAu chalcogen compound nanoparticles is basically the same as the process of adding metal M1, in that a compound of metal M2 is added as a precursor to the reaction system, mixed, and heated. Examples of Zn compounds that can serve as the metal M2 precursor include chlorides, sulfides, nitrates, acetates, sulfates, sulfamates, and stearates. Specifically, zinc chloride, zinc sulfide, zinc acetate, and zinc stearate can be used. In this case, the chalcogen compound described above may be added to the reaction system. The content of metal M2 in the semiconductor nanoparticles of the present invention is adjusted by the amount of metal M2 precursor added. The metal M2 compound is preferably added in solution form. While the intended amount of solution may be added in its entirety, it is preferable to add it dropwise in small amounts. If the rate of addition of metal M2 is too high, nanoparticles of metal M2 (Zn) alone may be produced separately from the target reaction. When adding the metal M2, a chalcogen compound can be added to the reaction system, and the same compound as the precursor of the chalcogen element described above may be added.

[0057] The heating temperature for adding metal M2 to AgAu chalcogen compound nanoparticles is preferably 50°C or higher and 250°C or lower. If the temperature is lower than 50°C, it becomes difficult for metal M2 to form a stable bond with AgAu chalcogen compound nanoparticles. On the other hand, if the temperature exceeds 250°C, decomposition of the semiconductor nanoparticles may occur. A more suitable reaction temperature is 80°C or higher and 150°C or lower. The heating time (reaction time) can be adjusted depending on the amount of each component charged in the reaction system, and is preferably 1 minute or higher and 120 minutes or lower. It is preferable to stir the reaction system.

[0058] By adding the compound of metal M2 and heating as described above, semiconductor nanoparticles made of an AgAu chalcogen compound in which metal M1 and metal M2 (Zn) are added to the AgAu chalcogen compound nanoparticles are produced. The produced semiconductor nanoparticles may be washed and recovered as appropriate, or may be used as is.

[0059] The semiconductor nanoparticles produced by the above steps have a protective agent bonded thereto. A preferred protective agent is an organic compound having 4 or more carbon atoms, and the semiconductor nanoparticles have dispersibility in low-polarity solvents. To impart dispersibility to the semiconductor nanoparticles in aqueous solvents, it is preferable to replace the protective agent bonded in the synthesis step with a hydrophilic protective agent.

[0060] One method for hydrophilizing semiconductor nanoparticles is to add the produced semiconductor nanoparticles to an organic solvent or water-soluble solvent such as alcohol, add a hydrophilic protective agent, and heat and stir the mixture. The hydrophilic protective agent is the organic compound having 3 or less carbon atoms as described above. The solvent used may be water, an alcohol such as ethanol, an ionic liquid, or the like.

[0061] As described above, the semiconductor nanoparticles according to the present invention are made of an AgAu chalcogen compound, and are obtained by adding metal M1 and metal M2 (Zn) to semiconductor nanoparticles of an AgAu chalcogen compound. The semiconductor nanoparticles according to the present invention exhibit favorable optical semiconductor properties and exhibit particularly favorable luminescence. Furthermore, the semiconductor nanoparticles according to the present invention are durable against replacement of a protective agent by ligand exchange to obtain dispersibility in an aqueous dispersion medium. Even when a hydrophilic protective agent is used, particle elution and deterioration of the optical semiconductor properties are suppressed, and favorable properties can be maintained.

[0062] The semiconductor nanoparticles according to the present invention are expected to be applied to biomarkers, etc. in addition to general semiconductor devices such as light-emitting elements, because their main constituent elements are biocompatible and low-toxicity elements. As described above, the semiconductor nanoparticles according to the present invention can acquire dispersibility in aqueous dispersion media, making them suitable for the aforementioned biouse.

[0063] Furthermore, the semiconductor nanoparticles according to the present invention have improved light emission and light absorption properties in the near-infrared region. In recent years, photoelectric conversion elements for which responsiveness in the near-infrared region is important include light receiving elements applied to LIDAR (Light Detection and Ranging) and near-infrared (SWIR) image sensors. The semiconductor nanoparticles according to the present invention are expected to be used in such photoelectric conversion elements operating in the near-infrared region.

[0064] TEM images of semiconductor nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) produced in the first embodiment. Absorption spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) produced in the first embodiment. Emission spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) produced in the first embodiment. TEM images of semiconductor nanoparticles (AgAuS@InS, AgAuS@InS@ZnS) after hydrophilization treatment in the first embodiment. XRD diffraction patterns of semiconductor nanoparticles (AgAuS@InS@ZnS) before and after hydrophilization in the first embodiment. Absorption spectra and emission spectra of semiconductor nanoparticles (AgAuS@InS) produced in the first embodiment before and after hydrophilization treatment. Absorption spectra and emission spectra of semiconductor nanoparticles (AgAuS@InS@ZnS) produced in the first embodiment before and after hydrophilization treatment. Emission decay of semiconductor nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS (before and after hydrophilization)) in the first embodiment. TEM images of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the second embodiment. XRD diffraction patterns of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the second embodiment. Absorption spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the second embodiment. Emission spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the second embodiment. TEM images of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the third embodiment. XRD diffraction patterns of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the third embodiment. Absorption spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the third embodiment. Emission spectra of semiconductor nanoparticles (AgAuS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in the third embodiment.

[0065] First Embodiment: Hereinafter, an embodiment of the present invention will be described. In this embodiment, semiconductor nanoparticles were produced from an AgAuS ternary compound as an AgAu chalcogen compound, and further, semiconductor nanoparticles were produced from the produced AgAuS multi-component compound to which In and Zn were added. The optical semiconductor properties of the synthesized semiconductor nanoparticles were evaluated, and further, changes in properties due to hydrophilization treatment were investigated.

[0066] [Production of AgAuS nanoparticles] 0.3 mmol of silver acetate (Ag(OAc)) as the Ag precursor, 0.1 mmol of chloro(dimethylsulfide)gold(I) as the Au precursor, and 0.2 mmol of thiourea as the chalcogen compound were weighed and placed in a test tube (Ag charge ratio (Ag / Au) was 3.0). Furthermore, 0.1 cm of 1-dodecanethiol (DDT) was used as a protective agent. ３ and 2.9 cm of oleylamine (OLA) as a solvent. ３ A stirrer was then placed in the test tube, and the air was replaced with nitrogen three times, followed by stirring with a hot stirrer for 10 minutes while heating at a reaction temperature of 150°C. After the reaction was completed, the mixture was allowed to cool for 30 minutes, then transferred to a small test tube and centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate.

[0067] Then, 4 cm of methanol was added to the supernatant as a poor solvent. ３ The mixture was added to form a precipitate, which was then centrifuged at 4,000 rpm for 5 minutes to recover the precipitate. ３ After adding and dispersing, the mixture was centrifuged under the same conditions to remove by-products and solvents for purification.

[0068] The precipitate obtained by the above procedure was dissolved in 3 cm of chloroform. ３ This dispersion was transferred to a sample bottle, and the atmosphere was replaced with nitrogen, and then the bottle was stored in a refrigerator in a dark place.

[0069] [Addition of In to AgAuS Nanoparticles] The above AgAuS nanoparticles 1.0 × 10 －７ 1.2 × 10 indium acetate as an In precursor was added to a dispersion containing 1.2 × 10 －５ mol and thioacetamide 1.8 × 10－５ A solution containing 1000 mol (solvent: oleylamine (3 cm ３ ) was added to the mixture, and the mixture was heated at 110°C for 15 minutes under stirring in a nitrogen atmosphere, thereby producing In-doped AgAuS nanoparticles (referred to as AgAuS@InS).

[0070] [Zn Addition to AgAuS Compound Nanoparticles] The In-doped AgAuS nanoparticles (AgAuS@InS) produced above were added with 2.5×10 zinc stearate as a Zn precursor. －５ mol and thioacetamide 2.5 × 10 －５ A solution containing 1000 mol (solvent: oleylamine (3 cm ３ )) was added at a drop rate of 3 cm ３ The addition was carried out over 1 hour at a rate of 1 / h. During the addition of Zn, the reaction system was stirred and maintained at 100°C under a nitrogen atmosphere. After the addition of Zn, the system was heated and maintained at 100°C for an additional 20 minutes while stirring. This resulted in the synthesis of Zn-doped AgAuS@InS nanoparticles (referred to as AgAuS@InS@ZnS).

[0071] [TEM Observation and Composition Analysis of Semiconductor Nanoparticles] TEM observation was performed on the AgAuS compound nanoparticles produced above. A Hitachi High-Technologies Corporation H-7650 TEM was used, and observations were performed at an accelerating voltage of 100 kV. Figure 1 shows TEM images of the AgAuS nanoparticles produced above, AgAuS@InS nanoparticles doped with In, and AgAuS@InS@ZnS nanoparticles doped with In and Zn (see the scale bar in each photograph for magnification). Each TEM image confirmed that approximately spherical nanoparticles were synthesized. The average particle diameters of the semiconductor nanoparticles were measured and calculated based on the TEM images: 2.1 nm for AgAuS nanoparticles, 3.0 nm for AgAuS@InS nanoparticles, and 4.0 nm for AgAuS@InS@ZnS nanoparticles. It is believed that the particle diameters increased sequentially as the AgAuS nanoparticles were coated (shelled) with In and Zn.

[0072] Furthermore, particle composition analysis of the nanoparticles was performed by EDX analysis using an energy dispersive X-ray analyzer (Emax Energy EX-250, manufactured by Horiba, Ltd.) attached to a scanning electron microscope (SU-1500, manufactured by Hitachi High-Technologies Corporation). The results are shown in Table 1 below. The results of the composition analysis are expressed in atomic % relative to the total nanoparticles. Table 1 also shows the ratio (x / (x+y)) of the number of Ag atoms to the sum of the number of Ag atoms (x) and the number of Au atoms (y), calculated based on the composition analysis results.

[0073]

[0074] As can be seen from Table 1, the Ag and Au contents naturally decrease as In and Zn are sequentially added to the AgAuS nanoparticles. However, it was confirmed that the ratio of Ag atoms (x / (x+y)) in each semiconductor nanoparticle (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) is almost constant.

[0075] [Measurement of Absorption Spectrum and Emission Spectrum] Next, the absorption spectrum of each semiconductor nanoparticle (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) was measured using a UV-visible spectrophotometer (Agilent 8453 manufactured by Agilent Technologies, Inc.) in the wavelength range of 400 nm to 1000 nm.

[0076] Furthermore, the emission spectrum and emission quantum efficiency of each semiconductor nanoparticle were measured. The emission spectrum was measured using a diode array spectrophotometer (PMA-12, C10027-02) manufactured by Hamamatsu Photonics K.K. The sample was dissolved in chloroform (n = 1.4429) and adjusted so that the absorbance at 600 nm was 0.1, and then the measurement was performed.

[0077] The luminescence quantum yield was measured using an absolute PL quantum yield measurement device (C9920-03, manufactured by Hamamatsu Photonics K.K.). When luminescence was observed at wavelengths longer than 1000 nm, the emission spectrum was measured using a multichannel spectrophotometer (PMA-12, manufactured by Hamamatsu Photonics K.K., model numbers: C10027-02 (wavelength range 350-1100 nm) and 10028-01 (wavelength range 900-1650 nm)). The sample was dissolved in chloroform (n=1.4429) and adjusted to an absorbance of 0.1 at 600 nm. The excitation light wavelength was 600 nm.

[0078] The measurement results of the absorption spectrum of each semiconductor nanoparticle (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) produced in this embodiment are shown in Figure 2. The measurement results of the emission spectrum and emission quantum yield are shown in Figure 3. The absorption edge wavelength (UV-λ), emission peak wavelength (PL-λ), and emission quantum efficiency (PLQY) for these results are shown in Table 2.

[0079]

[0080] 2 and Table 2, it can be said that there is no significant difference in the absorption spectra of the AgAuS compound nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS) produced in this embodiment, and it is confirmed that all semiconductor nanoparticles have an absorption edge wavelength of 750 nm or more. However, a slight shift in the spectrum to the longer wavelength side is observed in the semiconductor nanoparticles doped with In or Zn (AgAuS@InS, AgAuS@InS@ZnS).

[0081] On the other hand, the emission spectrum in Figure 3 shows that the addition of In and Zn to AgAuS nanoparticles has a favorable effect on emission. Looking at the quantum efficiency, AgAuS@InS, which is doped with only In, has an emission quantum efficiency nearly 10 times that of the base AgAuS. Furthermore, the emission quantum efficiency of AgAuS@InS@ZnS, which is further doped with Zn, is more than 20% higher than that of AgAuS@InS. In the present invention, the addition of Zn together with In is intended to improve durability by hydrophilizing the nanoparticles, but the additional addition of Zn is also thought to contribute to improving emission characteristics.

[0082] [HydrophiliZation Treatment by Protecting Agent Substitution] Next, the semiconductor nanoparticles produced in this embodiment were hydrophiliZed by replacing with a protective agent. The optical semiconducting properties of the hydrophiliZed semiconductor nanoparticles were then evaluated. The hydrophiliZation treatment Was performed on semiconductor nanoparticles in Which In Was added to AgAuS (AgAuS@InS) and semiconductor nanoparticles in Which In and Zn Were added to AgAuS (AgAuS@InS@ZnS). The hydrophiliZation treatment Was as folloWs.

[0083] 100 mm of tetramethylammonium hydroxide (TMAOH) was placed in a test tube. ３ , ethanol 900 mm ３ , 3-mercaptopropionic acid (MPA) 50 mm ３ Then, 1000 mm of a chloroform solution of semiconductor nanoparticles was added. ３ Then, a stirring bar was placed in the test tube, the inside of the test tube was replaced with nitrogen, and the test tube was heated and stirred at 70°C for 3 hours using a hot stirrer. After that, the solution was allowed to cool to room temperature, transferred to a small test tube, and then 3000mm acetone was added. ３ The supernatant was discarded, and the precipitate was dried. ３ was dispersed into

[0084] FIG. 4 shows TEM images of semiconductor nanoparticles (AgAuS@InS, AgAuS@InS@ZnS) before and after hydrophilization. It was confirmed that the particles of the semiconductor nanoparticles (AgAuS@InS) in which In was added to AgAuS were aggregated due to hydrophilization. The average particle size of the nanoparticles was not measurable. In contrast, the semiconductor nanoparticles (AgAuS@InS@ZnS) in which In and Zn were added to AgAuS showed some particle aggregation, but the nanoparticle state was maintained. Furthermore, no damage such as leaching was observed. The average particle size of the semiconductor nanoparticles (AgAuS@InS@ZnS) after hydrophilization was 4.1 nm.

[0085] Table 3 shows the results of composition analysis by EDX of semiconductor nanoparticles (AgAuS@InS@ZnS) before and after hydrophilization. Referring to Table 3, the Ag and Au contents are slightly reduced by hydrophilization. Furthermore, FIG. 5 shows the XRD diffraction patterns of the semiconductor nanoparticles (AgAuS@InS@ZnS) before and after hydrophilization. It can be said that there is no significant change in the diffraction pattern of the semiconductor nanoparticles before and after hydrophilization.

[0086]

[0087] Next, the absorption spectrum, emission spectrum, and emission quantum efficiency of the hydrophilized semiconductor nanoparticles (AgAuS@InS, AgAuS@InS@ZnS) were measured. The measurement method was the same as above. The measurement results for AgAuS@InS are shown in FIG. 6 , and the measurement results for AgAuS@InS@ZnS are shown in FIG. 7 . The absorption spectrum and emission spectrum of AgAuS@InS@ZnS ( FIG. 7 ) were measured for the semiconductor nanoparticles immediately after the hydrophilization treatment and for the semiconductor nanoparticles two weeks after the hydrophilization treatment.

[0088] As can be seen from Figure 6, the luminescence observed before hydrophilization did not occur in AgAuS@InS without Zn addition. As mentioned above, AgAuS@InS particles aggregated due to hydrophilization. It is believed that these changes in the semiconductor nanoparticles led to the loss of luminescence properties.

[0089] On the other hand, referring to FIG. 7 , in the case of AgAuS@InS@ZnS, in which Zn was added together with In, the absorption spectrum was almost the same as before the treatment. Furthermore, no significant changes due to hydrophilization were observed in the emission spectrum. Regarding the luminescence quantum efficiency, although it was slightly lower than before the hydrophilization treatment, it still showed favorable values ​​even after hydrophilization. Furthermore, the absorption spectrum and emission spectrum of the semiconductor nanoparticles (AgAuS@InS@ZnS) after hydrophilization remained unchanged even after two weeks, and in fact, the luminescence quantum efficiency increased. The absorption edge wavelength, emission peak wavelength, and luminescence quantum efficiency of AgAuS@InS@ZnS obtained from FIG. 7 are shown in Table 4. From the above results of the hydrophilization treatment, it can be said that the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment also have good stability after hydrophilization.

[0090]

[0091] Next, the luminescence lifetime of the luminescence was examined for the AgAuS compound nanoparticles (AgAuS, AgAuS@InS, AgAuS@InS@ZnS (before and after hydrophilization)) produced in this embodiment. The luminescence lifetime was examined by measuring the luminescence decay curve for each semiconductor nanoparticle. The luminescence decay curve was measured using a fluorescence lifetime measurement device (Quantaurus-Tau manufactured by Hamamatsu Photonics KK). The measurement was performed at room temperature, with excitation light of 445 nm. The average luminescence lifetime τ was then calculated from the obtained decay curve. The luminescence decay curve for each semiconductor nanoparticle is shown in FIG. 8, and the results are summarized in Table 5.

[0092]

[0093] From FIG. 8 and Table 4, it was confirmed that the semiconductor nanoparticles doped with In (AgAuS@InS) and with In and Zn (AgAuS@InS@ZnS) had an increased luminescence lifetime τ compared to the AgAuS nanoparticles that are the basis of the semiconductor nanoparticles of this embodiment. The luminescence lifetime τ was the longest at 8,805 ns (8.805 ms) for AgAuS@InS@ZnS doped with In and Zn of this embodiment. This semiconductor nanoparticle (AgAuS@InS@ZnS) showed an even longer luminescence lifetime τ (10,866 ns) after hydrophilization. However, the radiative recombination rate coefficient (k ｒａｄ ) is larger before hydrophilization.

[0094] Second embodiment: In this embodiment, semiconductor nanoparticles were produced and evaluated by adding In (metal M1) and Zn (metal M2) to AgAuS nanoparticles in a larger amount of Zn than in the first embodiment.

[0095] After synthesizing AgAuS nanoparticles and adding In in the same manner as in the first embodiment, the concentrations of the Zn compound and S compound in the solution at the time of adding Zn were changed. Zn was added by adding 5.0 × 10 zinc stearate to In-added AgAuS nanoparticles (AgAuS@InS). －５ mol and thioacetamide 5.0 × 10 －５ A solution containing 1000 mol (solvent: oleylamine (3 cm ３ The solution was added at a dropping rate of 3 cm, the same as in the first embodiment. ３ After the addition of the Zn compound solution, In- and Zn-doped AgAuS nanoparticles (AgAuS@InS@ZnS) were synthesized in the same manner as in the first embodiment.

[0096] The semiconductor nanoparticles (AgAuS@InS@ZnS) synthesized above were subjected to hydrophilization treatment in the same manner as in the first embodiment, under the same conditions and steps as in the first embodiment.

[0097] FIG. 9 is a TEM image of the semiconductor nanoparticles (AgAuS@InS@ZnS) produced in this embodiment. In this embodiment, roughly spherical nanoparticles were synthesized, and their shape did not change significantly even after hydrophilization. There was also no particle elution. The average particle size of the semiconductor nanoparticles in this embodiment was 4.5 nm before hydrophilization (synthesis stage) and 4.6 nm after hydrophilization. FIG. 10 shows the XRD diffraction pattern of the semiconductor nanoparticles in this embodiment.

[0098] Table 6 shows the results of EDX analysis of the composition of the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment. In this embodiment, the amount of Zn added was increased during synthesis. Compared to the semiconductor nanoparticles of the first embodiment, the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment have an increased Zn content.

[0099]

[0100] Next, the absorption spectrum and emission spectrum of the semiconductor nanoparticles (AgAuS@InS@ZnS) produced in this embodiment were measured. The measurement method and conditions were the same as those in the first embodiment. Figure 11 shows the measurement results of the absorption spectrum, and Figure 12 shows the measurement results of the emission spectrum. These results are summarized in Table 7.

[0101]

[0102] 11 and 12 and Table 7, the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment show the same tendency as in the first embodiment. That is, with regard to the emission spectrum, the semiconductor nanoparticles of this embodiment have good emission characteristics due to the addition of In and Zn to the AgAuS nanoparticles. It was also confirmed that the good emission characteristics can be maintained even after the protective agent is replaced by hydrophilization treatment.

[0103] Third embodiment: In this embodiment, semiconductor nanoparticles were produced and evaluated by adding In (metal M1) and Zn (metal M2) to AgAuS nanoparticles in the same amounts, but slowing down the rate at which Zn was added.

[0104] After synthesizing AgAuS nanoparticles and adding In in the same manner as in the first embodiment, the addition rate of the Zn precursor solution was changed. The Zn addition was performed using the same Zn precursor solution (zinc stearate 2.5 × 10 －５ mol and thioacetamide 2.5 × 10 －５ A solution containing 1000 mol (solvent: oleylamine (3 cm ３ ))) was used, and the solution was dropped at a rate of 1.5 cm ３ / h, which was lower than that of the first embodiment. After the addition of the Zn compound solution, In / Zn-doped AgAuS nanoparticles (AgAuS@InS@ZnS) were synthesized in the same manner as in the first embodiment. The synthesized semiconductor nanoparticles (AgAuS@InS@ZnS) were then subjected to a hydrophilization treatment in the same manner as in the first embodiment.

[0105] FIG. 13 is a TEM image of the semiconductor nanoparticles (AgAuS@InS@ZnS) produced in this embodiment. In this embodiment, roughly spherical nanoparticles were synthesized, and after hydrophilization, there was no elution of the particles and no significant change in shape. The average particle size of the semiconductor nanoparticles in this embodiment was 4.0 nm before hydrophilization (synthesis stage) and 5.2 nm after hydrophilization. FIG. 14 shows the XRD diffraction pattern of the semiconductor nanoparticles in this embodiment.

[0106] Table 8 shows the results of EDX analysis of the composition of the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment. The amounts of In and Zn added in this embodiment were the same as in the first embodiment, and no significant difference was observed in the composition.

[0107]

[0108] The absorption spectrum and emission spectrum of the semiconductor nanoparticles (AgAuS@InS@ZnS) produced in this embodiment were then measured. The measurement method and conditions were the same as those in the first embodiment. Figure 15 shows the measurement results of the absorption spectrum, and Figure 16 shows the measurement results of the emission spectrum. These results are summarized in Table 9.

[0109]

[0110] 15 and 16 and Table 9, it can be said that the semiconductor nanoparticles (AgAuS@InS@ZnS) of this embodiment basically have favorable characteristics similar to those of the first embodiment. With regard to the emission spectrum, the addition of In and Zn to the AgAuS nanoparticles allows the semiconductor nanoparticles of this embodiment to have favorable emission characteristics. In the semiconductor nanoparticles after hydrophilization, the degree of decrease in luminescence quantum efficiency was greater than in the first embodiment. However, even though the luminescence quantum efficiency decreased due to hydrophilization, the value was still favorable. It is believed that the semiconductor nanoparticles produced in this embodiment also did not deteriorate due to the hydrophilization treatment.

[0111] As described above, the semiconductor nanoparticles according to the present invention have suitable optical semiconductor properties. Furthermore, the semiconductor nanoparticles according to the present invention are suppressed from damage such as particle elution and performance degradation when subjected to protective agent substitution for hydrophilization. The semiconductor nanoparticles according to the present invention are expected to be applied to light-emitting elements and fluorescent materials used in display devices, etc., as well as photoelectric conversion elements and light-receiving elements mounted in solar cells, optical sensors, etc. Furthermore, the semiconductor nanoparticles according to the present invention are also useful as light-receiving elements applied to LIDAR and SWIR image sensors, where responsiveness in the near-infrared region is important. Furthermore, the semiconductor nanoparticles according to the present invention, which have good durability against hydrophilization, have good dispersibility in aqueous dispersion media, making them highly useful in biodevices.

Claims

1. Semiconductor nanoparticles consisting of a compound containing Ag, Au, a chalcogen element, metal M1, and metal M2, wherein the chalcogen element is at least one of S, Se, and Te, the metal M1 is at least one of In, Al, Ga, Tl, Cd, Hg, and Cu, and the metal M2 is Zn, and the compound has a total content of Ag, Au, the chalcogen element, metal M1, and metal M2 of 95 mass% or more.

2. The semiconductor nanoparticles according to claim 1, wherein the total content of metal M1 and metal M2 in the compound is 1 atomic % or more and 50 atomic % or less, and the ratio M1 / M2 of the content of metal M1 to the content of metal M2 is 0.5 or more and 1.5 or less.

3. The semiconductor nanoparticles according to claim 1 or 2, wherein the content of chalcogen elements in said compound is 30 atomic % or more and 60 atomic % or less.

4. Semiconductor nanoparticles according to claim 1 or 2, wherein the ratio of the number of Ag atoms to the sum of the number of Ag atoms x and the number of Au atoms y in the compound (x / (x+y)) is 0.50 or more and 0.90 or less.

5. A semiconductor nanoparticle according to claim 1 or 2, comprising: a core compound containing Ag, Au, and a chalcogen element; a first shell compound consisting of metal M1 or essentially containing metal M1 and containing at least one of Ag, Au, and a chalcogen element; and a second shell compound consisting of metal M2 or essentially containing metal M2 and containing at least one of Ag, Au, a chalcogen element, and metal M1, wherein the first shell compound coats at least a portion of the surface of the core compound, and the second shell compound coats at least a portion of the surface of the core compound and / or at least a portion of the surface of the first shell compound.

6. A semiconductor nanoparticle according to claim 1 or 2, comprising a core compound containing Ag, Au and a chalcogen element, and a third shell compound consisting of metal M1 and metal M2, or essentially containing metal M1 and metal M2 and containing at least one of Ag, Au and a chalcogen element, wherein the third shell compound covers at least a portion of the surface of the core compound.

7. The semiconductor nanoparticles according to claim 1 or 2, having an average particle size of 2 nm or more and 20 nm or less.

8. Semiconductor nanoparticles according to claim 1 or claim 2, having at least one of the following protective agents bonded to the surface: thiols having 3 or less carbon atoms, sulfides having 3 or less carbon atoms, disulfides having 3 or less carbon atoms, thioesters having 3 or less carbon atoms, and thioketones having 3 or less carbon atoms.

9. The semiconductor nanoparticles according to claim 1 or 2, wherein the absorption edge wavelength on the long wavelength side of the absorption spectrum is 600 nm or more.

10. The semiconductor nanoparticles according to claim 1 or 2, which have an emission spectrum with a peak wavelength of 700 nm or more.

Images