Semiconductor nanoparticles comprising AgAuSe-based multi-component compound

Abstract

The semiconductor nanoparticles according to the present invention comprise a compound containing Ag, Au, a chalcogen element essential to Se, and a metal M as essential constituent elements. Here, the metal M is at least one of Al, Ga, In, Tl, Zn, Cd, Hg, and Cu. In the compounds constituting the semiconductor nanoparticles according to the present invention, the total content of Ag, Au, a chalcogen element necessary for Se, and a metal M is 95 mass% or more. In addition, the content of the metal M in the compound is preferably 1-50 at% (inclusive). The semiconductor nanoparticles according to the present invention can exhibit good light absorption / emission characteristics in wavelength regions such as the near-infrared region and the short-wave infrared region.

Description

Technical Field

[0001] The present invention relates to semiconductor nanoparticles composed of an AgAuSe-based multinary compound, and more specifically, to semiconductor nanoparticles that are novel AgAuSe-based multinary compounds composed of Ag, Au, Se, and a metal M and have excellent optical semiconductor properties. Background Art

[0002] Semiconductors exhibit quantum confinement effects by becoming nanometer-scale tiny particles, showing a band gap corresponding to the particle size. Therefore, by controlling the composition and particle size of semiconductor nanoparticles to adjust the band gap, the emission wavelength or absorption wavelength can be set arbitrarily. Semiconductor nanoparticles that utilize this characteristic are also called quantum dots (QD: Quantum Dot), and are expected to be used in various technical fields. As examples of the application of semiconductor nanoparticles, for example, light-emitting elements and fluorescent substances used in display devices or labeling substances for detecting biological related substances are being studied. This is because, in addition to being able to control the emission wavelength by adjusting the particle size mentioned above, the emission peak width of semiconductor nanoparticles is also narrow enough and stable compared to organic pigments.

[0003] Furthermore, semiconductor nanoparticles not only allow for control of absorption wavelengths but also possess high quantum efficiency and a high absorption coefficient. Consequently, research is underway into the use of semiconductor nanoparticles in photoelectric conversion elements or light-receiving elements, such as those found in solar cells and various optical sensors. In particular, semiconductor nanoparticles are expected to be used as light-receiving elements in optical sensors that operate in the near-infrared (NIR) or short-wave infrared (SWIR) regions. These optical sensors, which operate in the long-wavelength region, are used in LIDAR (Light Detection and Ranging) or SWIR image sensors. LIDAR is a remote sensing system used in autonomous vehicles, drones, and ships, and has become crucial in the recent development of autonomous driving technology. SWIR image sensors are also expected to see increasing demand in areas such as food inspection, agriculture, and drones. Silicon thin films have been widely used as light-receiving elements in optical sensors to date. However, the sensitivity of sensors based on Si thin films decreases significantly in wavelengths above 900 nm, making them unsuitable for these applications. Therefore, there is a desire to develop light-receiving elements that utilize semiconductor nanoparticles.

[0004] As the specific composition of semiconductor nanoparticles studied so far, it is known that there are semiconductor nanoparticles composed of binary compound semiconductors such as Group 11-Group 16 compound semiconductors such as CdS, CdSe, CdTe, PbS, PbSe, Ag2S; and ternary compound semiconductors such as Group 11-Group 13-Group 16 compound semiconductors such as AgInTe2 (Patent Documents 1 to 4).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-243507

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2004-352594

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-014476

[0010] Patent Document 4: International Publication No. WO2020 / 054764 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] As mentioned above, semiconductor nanoparticles of various compositions are known, but they are still under research, and optimal semiconductor nanoparticles have not yet been found from a practical perspective. In particular, there are few semiconductor nanoparticles with suitable response characteristics for the near-infrared (NIR) and short-wave infrared (SWIR) regions.

[0013] Regarding the aforementioned conventional semiconductor nanoparticles, PbS nanoparticles can respond to near-infrared (NIR) and short-wave infrared (SWIR) radiation. However, Pb is included in the list of hazardous substances restricted for use in electrical and electronic equipment under the European RoHS Directive (Restriction of the use of certain Hazardous Substances in electrical and electronic equipment). Therefore, from an environmental perspective, it is difficult to say that it is a metal element that will be widely used in the future.

[0014] Furthermore, even for applications other than light-receiving elements such as photosensors, conventional semiconductor nanoparticles contain Cd in addition to Pb, and due to requirements such as biocompatibility (low-toxicity composition), usable semiconductor nanoparticles are limited.

[0015] Therefore, the present invention proposes semiconductor nanoparticles with a novel structure, not previously reported, that possess suitable optical semiconductor properties while also taking into account practical applications such as biocompatibility. In particular, the present invention proposes semiconductor nanoparticles that can respond to near-infrared (NIR) and short-wave infrared (SWIR) wavelengths and exhibit suitable light absorption and emission properties in these wavelength regions.

[0016] Means for solving problems

[0017] The present inventors have focused on semiconductor nanoparticles composed of chalcogenide compounds containing two metals (noble metals), Ag and Au, as new semiconductor nanoparticles. As shown in the above-mentioned prior art, nanoparticles of Ag chalcogenide compounds (Ag2S) are known to exhibit optical semiconductor properties. Au also has the same potential. Moreover, both Ag and Au noble metals are chemically relatively stable metals and have been known as biocompatible metals since ancient times. Therefore, it can be considered that the specific study of semiconductor nanoparticles containing ternary chalcogenide compounds of both Ag and Au has technical significance.

[0018] The present inventors further investigated the optimization of chalcogens that form compounds with Ag and Au. As a result, they confirmed that semiconductor nanoparticles composed of AgAuSe-based compounds, consisting of Ag, Au, and a chalcogen that necessarily includes Se (selenium), possess properties that contribute to solving the problems of the present invention.

[0019] According to the inventors' research, from the perspective of exploiting optical semiconductor properties alone, suitable semiconductor nanoparticles can be formed using an AgAuS ternary compound using S (sulfur) as the chalcogen. However, the inventors have confirmed that nanoparticles of the AgAuS ternary compound are insufficient for photoresponse in the near-infrared (NIR) and short-wave infrared (SWIR) regions, another objective of the present invention. Furthermore, the inventors have confirmed that the use of Se as the essential chalcogen enables photoresponse in the long-wavelength region.

[0020] Therefore, the present inventors studied the properties of semiconductor nanoparticles composed of AgAuSe-based compounds and found the optimal composition based on this. As a result, they discovered nanoparticles composed of AgAuSe-based multinary compounds in which a predetermined metal element (M) is added to the AgAuSe-based compound.

[0021] That is, the present invention that solves the above-mentioned problems is a semiconductor nanoparticle composed of a compound containing Ag, Au, a chalcogen element with Se as an essential component, and a metal M as an essential constituent element, wherein the metal M is at least any one of Al, Ga, In, Tl, Zn, Cd, Hg, and Cu, and the total content of Ag, Au, a chalcogen element with Se as an essential component, and the metal M in the compound is 95% by mass or more.

[0022] The following describes the composition and manufacturing method of semiconductor nanoparticles composed of AgAuSe-based multinary compound semiconductors according to the present invention. It should be noted that, for convenience, in this application specification, chalcogenide compounds composed of Ag, Au, and Se as an essential chalcogen are referred to as "AgAuSe-based compounds." Furthermore, the present invention also refers to quaternary or higher-element chalcogenide compounds in which at least one metal M is added to the AgAuSe-based compound.

[0023] A. Composition of semiconductor nanoparticles involved in the present invention

[0024] A-1. Chemical Composition of Semiconductor Nanoparticles

[0025] As described above, the semiconductor nanoparticles involved in the present invention are composed of AgAuSe-based multinary compounds formed by adding metal M to AgAuSe-based compounds. In the present invention, Ag and Au are metals necessary as metal elements (transition metal elements) constituting the basic compound AgAuSe-based compound of the present invention. Moreover, the properties of the AgAuSe-based multinary compound of the present invention vary depending on the presence ratio of Ag and Au in the compound. In the present invention, the ratio (x / (x+y)) of the number of atoms (x) of Ag in the compound constituting the nanoparticles to the total number of atoms (x) of Ag and the number of atoms (y) of Au is preferably 0.20 or more and 0.95 or less. The ratio of the number of atoms of Ag is more preferably 0.40 or more, further preferably 0.5 or more, and particularly preferably 0.6 or more. In addition, the ratio of the number of atoms of Ag is more preferably 0.90 or less, further preferably 0.88 or less. Within these composition ranges, the effect of increasing the luminous quantum efficiency, etc. becomes obvious.

[0026] In addition, Se is also a necessary constituent element of the AgAuSe-based multinary compound of the present invention. In the present invention, Se is selected as a chalcogen to impart effective photoresponse characteristics to semiconductor nanoparticles in both the near-infrared region (NIR) and the short-wave infrared region (SWIR). The AgAuS ternary compound using S as a chalcogen shows effective photoresponse characteristics / luminescence peaks in a wavelength region around 800 nm, but tends to attenuate in a wavelength region above 900 nm. In the present invention, by using Se as a necessary chalcogen, suitable photoresponse characteristics / luminescence peaks can be shown even in a wavelength region above 900 nm. It is speculated that this effect occurs because the orbital energy difference between each metal and chalcogen in the compound is reduced by using Se, which has a mass greater than S.

[0027] Se is included in the AgAuSe-based multinary compound to compensate for the charge of Ag, Au, and the metal M. Therefore, the content of Se-based chalcogens varies depending on the content or valence of Ag, Au, and the metal M. The content of Se-based chalcogens in the AgAuSe-based multinary compound is preferably 25 atomic % to 60 atomic %. More preferably, the content of Se-based chalcogens is 30 atomic % to 45 atomic %.

[0028] Furthermore, in the present invention, the metal M added to improve the properties of the AgAuSe-based compound is at least one of Al, Ga, In, Tl, Zn, Cd, Hg, and Cu, elements belonging to Groups 11 to 13. These metal elements produce changes in the properties of the AgAuSe-based compound, such as an improvement in the luminescence quantum efficiency and a shift in the absorption wavelength. More preferred metals M include In, Cu, Zn, and Ga.

[0029] The AgAuSe-based multinary compound constituting the semiconductor nanoparticles of the present invention changes its structure and properties depending on the type and content of the metal M. The content of the metal M in the compound is preferably not less than 1 atomic % and not more than 50 atomic %. When the content of the metal M is less than 1 atomic %, there is essentially no change from the AgAuSe-based compound. In addition, when it exceeds 50 atomic %, the effect of improving properties such as quantum efficiency is greatly reduced. Moreover, in the case where the metal M is an element belonging to Group 13 elements such as Al, Ga, In, the content of the metal M is more preferably set to not less than 1 atomic % and not more than 15 atomic %.

[0030] The semiconductor nanoparticles involved in the present invention are composed of AgAuSe-based multinary compounds with Ag, Au, Se as essential chalcogens, and metal M as essential constituent elements. In the AgAuSe-based multinary compound, the total content of Ag, Au, Se as essential chalcogens, and metal M is 95% by mass or more relative to the entire compound. As elements that may be included in addition to the essential constituent elements Ag, Au, Se, and metal M, Ge, Si, Sn, Pb, O, etc. can be considered, and these elements are allowed if they are less than 5% by mass. However, in the compound, the total content of Ag, Au, Se as essential chalcogens, and metal M is preferably 99% by mass or more, more preferably 99.9% by mass or more. It should be noted that the composition value of the compound here is the value of the AgAuSe-based multinary compound constituting the semiconductor nanoparticles, and does not include the components of the protective agent described later.

[0031] It should be noted that the AgAuSe-based multinary compound constituting the semiconductor nanoparticles of the present invention contains Se as an essential chalcogen element and may therefore contain chalcogen elements other than Se, such as S. For example, in the manufacturing process of the semiconductor nanoparticles described later, when a chalcogen element other than Se is used during doping with the metal M, semiconductor nanoparticles containing Se and S are sometimes formed. However, from the perspective of light responsiveness and luminescence quantum efficiency in the long wavelength region, a particularly preferred embodiment is semiconductor nanoparticles of an AgAuSe-based multinary compound containing only Se as a chalcogen element. Moreover, the preferred range of the Se content in this case is the same as the preferred range of the chalcogen content described above.

[0032] A-2. Structure of semiconductor nanoparticles according to the present invention

[0033] Regarding the structure of the semiconductor nanoparticles composed of the AgAuSe-based multinary compound of the present invention, there is no particular limitation on the distribution state of the atoms of Ag, Au, Se, and metal M, which are the constituent elements. Examples of the structure of the compound constituting the semiconductor nanoparticles include compounds in which AgAuSe-based compounds containing Ag, Au, and Se are doped with metal M. Doping in this case refers to a state in which metal M atoms replace the crystal lattice of the semiconductor compound crystal composed of the AgAuSe-based compound and / or invade the lattice space.

[0034] In addition, the compound constituting the semiconductor nanoparticles of the present invention can be constituted by a single phase or by a plurality of phases. The particles constituted by a plurality of phases can also adopt a so-called core-shell structure. In the core-shell structure, sometimes there is the following structure: the AgAuSe system compound comprising Ag, Au, and Se becomes the compound (core compound) as the core, and the metal M, or the compound that must comprise metal M and comprise at least any one of Ag, Au, and Se becomes the shell (shell compound) and covers at least a portion of the surface of the core compound. About the semiconductor nanoparticles of the core-shell structure, it is believed that the surface defects of the AgAuSe system compound as the core are modified by the metal M in the shell, so that the characteristics of the AgAuSe system compound are improved. In this case, the shell compound can be constituted by only metal M, or by a compound (such as AgMSe2) of metal M and at least any one of Ag, Au, and Se, or by a mixture thereof. In any of these structures, the element distribution in the AgAuSe system polynary compound as the semiconductor nanoparticle can be regular or irregular.

[0035] It should be noted that a scanning transmission electron microscope (Scanning TEM) can be appropriately used in the composition and structural analysis of the semiconductor nanoparticles involved in the present invention. In particular, a high-angle scattering annular dark field scanning transmission microscope (HAADF-STEM) can obtain a scattering image reflecting the composition information of the nanoparticles. By combining it with an energy dispersive X-ray spectrometer (EDX), the distribution state of Ag, Au, Se, and metal M and the overall composition of the nanoparticles can be understood.

[0036] The average particle size of the semiconductor nanoparticles to which the present invention relates is preferably 2 nm or more and 20 nm or less. The particle size of the semiconductor nanoparticles is related to the adjustment of the band gap caused by the quantum confinement effect. In order to exert suitable luminescence / light absorption characteristics by adjusting the band gap, it is preferably set to the above-mentioned average particle size. It should be noted that the average particle size of the semiconductor nanoparticles can be obtained by observing a plurality of (preferably more than 100) particles using an electron microscope such as a TEM, measuring the particle size of each particle, and calculating the particle number average.

[0037] A-3. Optical semiconductor properties of semiconductor nanoparticles according to the present invention

[0038] As mentioned above, semiconductor nanoparticles adjust the band gap by the quantum confinement effect according to particle diameter, thereby light absorption characteristics are changed. In the semiconductor nanoparticles to which the present invention relates, the absorption end wavelength on the long wavelength side of the absorption spectrum is preferably set to more than 800nm. Thus, semiconductor nanoparticles have absorptivity / responsiveness to light from the visible light region to the near-infrared region. In the present invention, as a more preferred embodiment, the absorption end wavelength on the long wavelength side of the absorption spectrum can be the semiconductor nanoparticles more than 850nm. In addition, in the mensuration of the luminescence spectrum of the semiconductor nanoparticles to which the present invention relates, it is preferred that the peak wavelength of the luminescence spectrum appear in a wavelength region longer than 900nm, and it is more preferred that the peak wavelength appear in a wavelength region longer than 1000nm.

[0039] A-4. Methods of using the semiconductor nanoparticles of the present invention

[0040] By coating / loading the semiconductor nanoparticles according to the present invention onto a suitable substrate / carrier, the semiconductor nanoparticles can be applied to the above-mentioned various uses such as light-emitting elements. There are no particular restrictions on the composition or shape / size of the substrate or carrier. As a plate-like or foil / film substrate, for example, glass, quartz, silicon, ceramics or metals can be exemplified. In addition, as granular / powdered carriers, inorganic oxides such as ZnO, TiO 2 , WO 3 , SnO 2 , In 2 O 3 , Al 2 O 3 can be exemplified. In addition, the semiconductor nanoparticles can also be loaded onto the above-mentioned inorganic oxide carrier and then fixed on the substrate.

[0041] In addition, when semiconductor nanoparticle is coated / loaded on base material / carrier, as mentioned above, use semiconductor nanoparticle mostly to be dispersed in the solution / slurry / ink that forms in the suitable dispersion medium.As the dispersion medium of this solution etc., can use chloroform, toluene, hexanaphthene, hexane etc.And, as the coating method of the solution of semiconductor nanoparticle etc., can use dipping, spin coating, as the method for load, can use whole bag of trickles such as dropping method, impregnation method, adsorption method in addition.

[0042] It should be noted that, in order to suppress aggregation during the synthesis process or when dispersed in the dispersion medium as described above, the semiconductor nanoparticles of the present invention preferably contain a protective agent. As the protective agent, at least any one of the following is preferred: an alkylamine having an alkyl chain carbon number of 4 or more and 20 or less, an alkenylamine having an alkenyl chain carbon number of 4 or more and 20 or less, an alkylcarboxylic acid having an alkyl chain carbon number of 3 or more and 20 or less, an alkenylcarboxylic acid having an alkenyl chain carbon number of 3 or more and 20 or less, an alkanethiol having an alkyl chain carbon number of 4 or more and 20 or less, a trialkylphosphine having an alkyl chain carbon number of 4 or more and 20 or less, a trialkylphosphine oxide having an alkyl chain carbon number of 4 or more and 20 or less, triphenylphosphine, or triphenylphosphine oxide. These protective agents bind to the surface of the semiconductor nanoparticles and cover at least a portion thereof, suppressing aggregation of the semiconductor nanoparticles in the dispersion and forming a uniform solution. In addition, in the synthesis step of the semiconductor nanoparticles, the protective agent is added to the reaction system together with the raw materials to synthesize nanoparticles with a suitable average particle size. It should be noted that the protective agent may be the above-mentioned alkylamines, alkenylamines, alkylcarboxylic acids, alkenylcarboxylic acids, alkanethiols, trialkylphosphines, trialkylphosphine oxides, triphenylphosphine, triphenylphosphine oxide, alone or in combination.

[0043] B. Method for producing semiconductor nanoparticles according to the present invention

[0044] Next, the manufacturing method of the semiconductor nanoparticles to which the present invention relates is described. The semiconductor nanoparticles of the present invention are composed of AgAuSe-based polynary compounds doped with metal M in AgAuSe-based compounds. Regarding the manufacturing method of the nanoparticles of the AgAuSe-based polynary compounds, first, a method for synthesizing the AgAuSe-based polynary compounds by simultaneously reacting precursors (Ag precursor, Au precursor, Se precursor, metal M precursor) containing each element of Ag, Au, Se, and metal M can be listed (this synthesis method is sometimes referred to as direct synthesis). In addition, as the second manufacturing method, there are nanoparticles of synthetic AgAuSe-based compounds, a method for synthesizing the AgAuSe-based polynary compounds by adding / doping metal M in the nanoparticles (this synthesis method is sometimes referred to as 2-stage synthesis). Below, the manufacturing method of the semiconductor nanoparticles using each synthesis method is described.

[0045] B-1. Method for producing semiconductor nanoparticles by direct synthesis

[0046] When producing AgAuSe-based multi-component compound nanoparticles by direct synthesis, an Ag precursor, an Au precursor, a Se precursor, and a metal M precursor are mixed in a reaction solvent, and the reaction system composed of these is heated at a temperature of 30°C to 200°C.

[0047] As the Ag precursor and Au precursor that become raw materials, Ag salt or Ag complex, Au salt or Au complex are applied respectively. Ag precursor and Au precursor are preferably salts or complexes that comprise monovalent Ag or monovalent Au. However, for Au precursor, a precursor that comprises trivalent Au is sometimes used. This is because, in the building-up process of semiconductor nanoparticles, trivalent Au is reduced to monovalent Au by solvent or coexisting Se precursor etc.

[0048] Preferred Ag precursors include silver acetate (Ag(OAc)), silver nitrate, silver carbonate, silver oxide, silver oxalate, silver chloride, silver iodide, silver cyanide (I) salt, and silver diethyldithiocarbamate. Preferred Au precursors include chloro(dimethylsulfide)gold(I) ((CH3)2SAuCl), Au resinate (C 10 H 18 Au2S2: CAS68990-27-2), gold (I) iodide, gold (I) sulfite, chloroauric acid (III), gold (III) acetate, gold (I) cyanide, gold (III) cyanide, 1,10-phenanthroline gold (III), etc.

[0049] In addition, as Se compounds serving as Se precursors, in addition to powdered selenium, Se compounds such as selenourea (Se=C(NH2)2), selenocysteine, trioctylphosphine selenide, triphenylphosphine selenide, diphenyl diselenide, and dibenzyl diselenide can also be used.

[0050] Examples of the compound serving as a precursor of the metal M include chlorides, sulfides, nitrates, acetates, sulfates, sulfamates, and stearates of the metal M. Examples include indium chloride, indium acetate, indium diethyldithiocarbamate, copper chloride, copper acetate, zinc stearate, and zinc acetate.

[0051] The composition of the synthesized AgAuSe-based polynary compound can be adjusted by the ratio of the input amount of the Ag precursor to the Au precursor. When the atomic number of the Ag atoms in the Ag precursor is set to a and the atomic number of the Au atoms in the Au precursor is set to b, it is preferred that the input amounts of the Ag precursor and the Au precursor for obtaining a suitable AgAuSe-based polynary compound be set to a ratio of the atomic number of the Ag atoms relative to their total (a / (a+b): hereinafter sometimes referred to as the Ag input ratio) be 0.20 or more and 0.95 or less. The Ag input ratio is more preferably 0.4 or more.

[0052] It should be noted that the amount of Se precursor added to the reaction system can be set within a wide range relative to the amount of Ag, Au, and metal M. This is because, even if there is excess Se in the reaction system, the effect on the composition of the AgAuSe-based multi-component compound is minimal.

[0053] In addition, as mentioned above, semiconductor nanoparticles of the present invention are preferably combined with protective agent in AgAuSe system polynary compound.Therefore, in above-mentioned reaction system, preferably add protective agent together with Ag precursor, Au precursor etc.As protective agent, preferably add at least any one in following: alkylamine that alkyl chain carbon number is more than 4 and less than 20, alkenylamine that alkenyl chain carbon number is more than 4 and less than 20, alkylcarboxylic acid that alkyl chain carbon number is more than 3 and less than 20, alkenylcarboxylic acid that alkyl chain carbon number is more than 3 and less than 20, alkylthiol that alkyl chain carbon number is more than 4 and less than 20, trialkylphosphine that alkyl chain carbon number is more than 4 and less than 20, trialkylphosphine oxide, triphenylphosphine, triphenylphosphine oxide that alkyl chain carbon number is more than 4 and less than 20.

[0054] It should be noted that, although the reaction system in the synthesis of semiconductor nanoparticles can generate nanoparticles without a solvent, it is preferred to use a solvent. When a solvent is used, octadecene, tetradecane, oleic acid, oleylamine, dodecanethiol or a mixture thereof can be used.

[0055] Then, by heating the reaction system consisting of an Ag precursor, an Au precursor, a Se precursor, a metal M precursor and a protective agent, AgAuSe-based multinary compound nanoparticles are synthesized. The heating temperature (reaction temperature) at this time is set to be above 30°C and below 200°C. When it is below 30°C, it is difficult to synthesize AgAuSe-based multinary compounds. On the other hand, when it exceeds 200°C, there are problems such as Au forming nanoparticles alone and failing to generate compounds of the desired composition. The average particle size of the semiconductor nanoparticles increases with the increase of the reaction temperature, but as long as it is within the above-mentioned temperature range, it rarely exceeds the preferred average particle size. A more preferred reaction temperature is above 40°C and below 120°C.

[0056] In addition, reaction time (heating time) can be adjusted according to the input amount of raw materials, and is preferably set to more than 5 minutes and less than 120 minutes. Reaction time is more preferably set to more than 10 minutes, and further preferably set to more than 15 minutes. It should be noted that, in the synthesis reaction of semiconductor nanoparticles, the reaction system is preferably stirred.

[0057] After the synthesis reaction of the semiconductor nanoparticles is completed, the reaction system is cooled as needed to recover the semiconductor nanoparticles. In this case, the nanoparticles are precipitated by adding an alcohol (ethanol, methanol, etc.) as a poor solvent, or the semiconductor nanoparticles are precipitated and recovered by centrifugation, and the particles are further temporarily washed with an alcohol (ethanol, methanol, etc.) and then uniformly dispersed in a good solvent such as chloroform.

[0058] B-2. Method for producing semiconductor nanoparticles using two-stage synthesis

[0059] The semiconductor nanoparticles of the AgAuSe-based multinary compound according to the present invention can also be produced by doping AgAuSe-based compound nanoparticles with a metal M. In this case, after synthesizing the AgAuSe-based compound, a metal M precursor is reacted to synthesize the AgAuSe-based multinary compound.

[0060] Nanoparticles of the AgAuSe compound can be synthesized by mixing an Ag precursor, an Au precursor, and a Se precursor in a reaction solvent and heating the reaction system composed of them at a temperature of 30° C. to 200° C.

[0061] The Ag precursor, Au precursor, and Se precursor used as raw materials for the AgAuSe-based compound can use the same metal salts and metal complexes as those used in the direct synthesis of the AgAuSe-based multinary compound. Furthermore, the amounts of the Ag precursor, Au precursor, and Se precursor used in the synthesis of the AgAuSe-based compound can also be the same as those used in the direct synthesis of the AgAuSe-based multinary compound. Furthermore, the use of solvents or protective agents used to form the reaction system can also be set in the same manner as those used in the direct synthesis of the AgAuSe-based multinary compound.

[0062] The heating temperature (reaction temperature) of the reaction system consisting of an Ag precursor, an Au precursor, a Se precursor and a protective agent is set to be above 30°C and below 200°C. When it is below 30°C, it is difficult to synthesize the AgAuSe-based compound. A more preferred reaction temperature is above 40°C and below 120°C. In addition, the heating time (reaction time) is preferably set to be above 1 minute and below 120 minutes. After the synthesis reaction of the semiconductor nanoparticles of the AgAuSe-based compound is completed, it can be recovered in the same manner as above and then provided for doping of the metal M.

[0063] It should be noted that the AgAuSe-based compound nanoparticles synthesized as described above are compounds represented by the composition formulas of Ag1Au7Se4, AgAu3Se2, Ag3Au5Se4, AgAuSe, Ag5Au3Se4, Ag3AuSe2, and Ag7AuSe4, or compounds similar to these composition formulas. However, in addition to the compounds having the aforementioned stoichiometric compositions, compounds having compositions other than the aforementioned stoichiometric compositions may also be listed. These compositions may be stoichiometric, non-stoichiometric, or a mixture thereof.

[0064] The doping of the AgAuSe compound with the metal M can be performed in the absence of a solvent, but is preferably performed in a solvent. The solvent used in the reaction system for the AgAuSe compound can be the same solvent as that used in the reaction system for the AgAuSe compound. The reaction system containing the nanoparticles of the AgAuSe compound produced above can be used directly, or the nanoparticles can be recovered using the separation method described above and then dispersed in a solvent to form a reaction system.

[0065] In the step of adding the metal M to the AgAuSe-based compound nanoparticles, a metal M compound is added / mixed into the reaction system as a metal M precursor and then heated. The metal M precursor can be the same metal salt or metal complex as used in the direct synthesis of the AgAuSe-based multinary compound. The preferred range of the amount of the metal M precursor added to the reaction system is also the same as for the direct synthesis.

[0066] Furthermore, when doping with the metal M in the two-stage synthesis, a chalcogen can be added to the reaction system along with the metal M precursor to compensate for the charge that converts the AgAuSe-based compound into an AgAuSe-based multinary compound. The chalcogen in this case is not limited to Se; S can also be added. For example, in addition to elemental sulfur, compounds such as thiourea, alkylthiourea, thioacetamide, and alkanethiols; β-dithioketones, dithiols, xanthates, and diethyldithiocarbamates can be added. However, the addition of a chalcogen when doping the AgAuSe-based compound nanoparticles with the metal M is not essential.

[0067] The doping of metal M is carried out by heating a reaction system containing an AgAuSe-based compound, a metal M precursor, and an optionally added chalcogen element. The heating temperature at this time is preferably set to be above 30°C and below 200°C. When it is below 30°C, the doping of metal M is difficult. On the other hand, when it exceeds 200°C, decomposition of the AgAuSe-based compound may occur. A more preferred reaction temperature is above 100°C and below 150°C. In addition, the heating time (reaction time) can be adjusted according to the input amount of each component in the reaction system, and is preferably set to be above 5 minutes and below 60 minutes. It should be noted that the reaction system is preferably stirred.

[0068] Semiconductor nanoparticles composed of an AgAuSe-based multi-component compound can be synthesized by the reaction step of adding the metal M. Thereafter, the semiconductor nanoparticles can be recovered in the same manner as in the direct synthesis production method.

[0069] Effects of the Invention

[0070] As described above, the present invention is a semiconductor nanoparticle composed of an AgAuSe-based multinary compound to which a metal M is added. The AgAuSe-based compound exhibits optical semiconductor properties when formed into nanoparticles, and exhibits more suitable properties by adding a metal M such as In.

[0071] Since the semiconductor nanoparticles composed of the AgAuSe-based multinary compound of the present invention are mainly composed of biocompatible, low-toxic elements, they are expected to be used not only in general semiconductor devices such as light-emitting elements but also in bioavailable markers.

[0072] Furthermore, the semiconductor nanoparticles of the present invention achieve improved light emission and absorption properties in the near-infrared region. In recent years, photoelectric conversion elements that prioritize responsiveness in the near-infrared region have been used in light-receiving elements of LIDAR and SWIR image sensors. The semiconductor nanoparticles of the present invention are expected to be used in photoelectric conversion elements operating in such near-infrared regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] [ Figure 1 ]TEM images of semiconductor nanoparticles of Examples 1 and 2 (AgAuSeIn) of the first embodiment, Reference Example 1 (AgAuSe), and Reference Example 2 (AgAuS).

[0074] [ Figure 2 ]Absorption spectra of semiconductor nanoparticles of Example 1 and Example 2 (AgAuSeIn) of the first embodiment.

[0075] [ Figure 3 ]Absorption spectra of semiconductor nanoparticles of Reference Example 1 (AgAuSe) and Reference Example 2 (AgAuS) of the first embodiment.

[0076] [ Figure 4 ]Luminescence spectra of semiconductor nanoparticles of Example 1 and Example 2 (AgAuSeIn) of the first embodiment.

[0077] [ Figure 5 ]The luminescence spectra of Reference Example 1 (AgAuSe) and Reference Example 2 (AgAuS) of the first embodiment.

[0078] [ Figure 6 ]TEM image of AgAuSeIn nanoparticles synthesized by adjusting the In input amount in the second embodiment.

[0079] [ Figure 7 ]Measurement results of the absorption spectrum of AgAuSeIn nanoparticles synthesized by adjusting the In input amount in the second embodiment.

[0080] [ Figure 8 ]Luminescence spectrum of AgAuSeIn nanoparticles synthesized by adjusting the In input amount in the second embodiment.

[0081] [ Figure 9a ]TEM image of AgAuSeIn nanoparticles synthesized in the third embodiment by adjusting the Ag input ratio and with a reaction time of 20 minutes.

[0082] [ Figure 9b ]TEM image of AgAuSeIn nanoparticles synthesized in the third embodiment by adjusting the Ag input ratio and with a reaction time of 10 minutes.

[0083] [ Figure 10a ]Absorption spectrum of AgAuSeIn nanoparticles synthesized in the third embodiment by adjusting the Ag input ratio and with a reaction time of 20 minutes.

[0084] [ Figure 10b ]Absorption spectrum of AgAuSeIn nanoparticles synthesized in the third embodiment by adjusting the Ag input ratio and with a reaction time of 10 minutes.

[0085] [ Figure 11a ] In the third embodiment, the luminescence spectrum of AgAuSeIn nanoparticles synthesized by adjusting the Ag input ratio and with a reaction time of 20 minutes.

[0086] [ Figure 11b ] In the third embodiment, the luminescence spectrum of AgAuSeIn nanoparticles synthesized by adjusting the Ag input ratio and with a reaction time of 10 minutes.

[0087] [ Figure 12 ] XRD diffraction patterns of AgAuSeIn nanoparticles synthesized in the third embodiment with the Ag input ratio set to 0.5 and 0.75 (reaction time 20 minutes and 10 minutes).

[0088] [ Figure 13 ]TEM image of AgAuSeIn nanoparticles synthesized by adjusting the reaction time in the fourth embodiment.

[0089] [ Figure 14 ]Absorption spectrum of AgAuSeIn nanoparticles synthesized by adjusting the reaction time in the fourth embodiment.

[0090] [ Figure 15 ]Luminescence spectrum of AgAuSeIn nanoparticles synthesized by adjusting the reaction time in the fourth embodiment.

[0091] [ Figure 16 ] XRD diffraction patterns of AgAuSeIn nanoparticles synthesized by setting the reaction time to 0.5 and 0.75 in the fourth embodiment. DETAILED DESCRIPTION

[0092] First embodiment The following describes an embodiment of the present invention. In this embodiment, semiconductor nanoparticles composed of an AgAuSe-based multinary compound (AgAuSeIn) containing In as the metal M were synthesized using the two synthesis methods described above. Their composition was then analyzed, and their photoresponse characteristics were evaluated.

[0093] Example 1 In this example, AgAuSeIn nanoparticles were synthesized via direct synthesis. 0.075 mmol of silver acetate (Ag(OAC)) as an Ag precursor, 0.025 mmol of gold(I) chloride (dimethylsulfide) as an Au precursor, 0.10 mmol of indium acetate (In(OAC)3) as an In precursor for the metal M, and 0.20 mmol of selenourea as a Se precursor were placed in a test tube. 2.9 mL of oleylamine (OLA) as a solvent and 0.1 mL of 1-dodecanethiol (DDT) as a protective agent were added.

[0094] A stirrer was placed in a test tube containing the above raw materials and solvent, and nitrogen was purged three times. The reaction temperature was then set to 50°C using a thermostirrer and heated for 10 minutes while stirring. After the reaction was completed, the mixture was allowed to cool for 20 minutes, then transferred to a small test tube and centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate.

[0095] Then, 4 cm 3 Methanol as a poor solvent produced a precipitate, which was centrifuged at 4000 rpm for 5 minutes and recovered. 4 cm 3 After being dispersed in ethanol, the nanoparticles of the AgAuSeIn compound were purified by centrifugation under the same conditions to remove by-products and the solvent.

[0096] The nanoparticles of the AgAuSeIn compound obtained by the above operation were dispersed in a 3 cm 3A dispersion of AgAuSeIn semiconductor nanoparticles was obtained in chloroform. The dispersion was transferred to a sample bottle, purged with nitrogen, and then stored in a refrigerated container shielded from light.

[0097] Example 2 In this example, AgAuSeIn nanoparticles were synthesized by a two-stage synthesis. In this example, nanoparticles of AgAuSe, which is an AgAuSe-based compound, were first synthesized, and then doped with In to synthesize nanoparticles of AgAuSeIn.

[0098] To synthesize AgAuSe nanoparticles, 0.3 mmol of silver acetate (Ag precursor), 0.1 mmol of gold(I) chloride (dimethylsulfide) (Au precursor), and 0.20 mmol of selenourea (Se precursor) were placed in a test tube. Furthermore, 2.9 mL of oleylamine (solvent) and 0.1 mL of 1-dodecanethiol (protecting agent) were added.

[0099] After nitrogen purge, the reaction was heated to 50°C for 10 minutes using a thermomixer while stirring. After the reaction was complete, the mixture was allowed to cool for 20 minutes before being transferred to a small test tube. The supernatant and precipitate were separated by centrifugation at 4000 rpm for 5 minutes. Recovery and purification were then performed as in Example 1 to obtain AgAuSe nanoparticles.

[0100] Then, the AgAuSe nanoparticles 1.0×10 -5 mmol, indium chloride (InCl3) as an In precursor 4.13×10 -6 mol, and thioacetamide as an S compound 6.19×10 -6 mol was mixed with 3.0 mL of dehydrated oleylamine as a solvent and heated to dope the AgAuSe nanoparticles with In. The heating temperature was set to 110°C for 15 minutes. After the reaction was completed, the mixture was allowed to cool for 20 minutes, then transferred to a small test tube and centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate. Purification was then performed in the same manner as above to recover the AgAuSe(S)In nanoparticles, and a dispersion was prepared in the same manner as in Example 1.

[0101] Reference Example 1 In order to confirm the effect of doping the AgAuSe compound with In (metal M), the nanoparticles of the AgAuSe compound synthesized in Example 2 were evaluated without doping with In.

[0102] Reference Example 2 Nanoparticles of an AgAuS ternary compound using S as a chalcogen element forming a compound with Ag and Au were synthesized as follows.

[0103] 0.3 mmol of silver acetate as an Ag precursor, 0.1 mmol of chloro(dimethylsulfide)gold(I) as an Au precursor, and 0.2 mmol of thiourea as an S precursor were placed in a test tube, and 2.9 mL of oleylamine as a solvent and 0.1 mL of 1-dodecanethiol as a protective agent were added.

[0104] After nitrogen substitution as above, the reaction temperature was set to 150°C using a thermostirrer and heated for 10 minutes while stirring. 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.

[0105] Then, centrifugal separation and purification were performed in the same manner as in Example 1, etc., to obtain a dispersion of nanoparticles of the AgAuS ternary compound.

[0106] [TEM observation and measurement of average particle size]

[0107] TEM observation was performed on the nanoparticles of Examples 1 and 2 (AgAuSeIn), Reference Example 1 (AgAuSe), and Reference Example 2 (AgAuS). Figure 1 Shown are the TEM images (magnification with reference to the scale bar of each photograph) of each semiconductor nanoparticle manufactured.Confirm that roughly spherical nanoparticles have been synthesized from each TEM image.Then, based on the TEM image, measure and calculate the average grain size of the nanoparticles of each composition.In particle diameter determination, obtain particle diameter for whole measurable nanoparticles included in the TEM image, calculate average grain size.

[0108] [Composition Analysis of Nanoparticles]

[0109] EDX analysis was performed simultaneously with the above-mentioned TEM observation to perform composition analysis of the nanoparticles. The measurement results of the composition of each semiconductor nanoparticle are shown in Table 1. In this embodiment and each of the following embodiments, the results of the composition analysis are expressed as atomic % relative to the entire nanoparticles. In addition, the ratio (x / (x+y)) of the number of Ag atoms (x) calculated based on the composition analysis results to the total number of Ag atoms (x) and the number of Au atoms (y) is also shown in Table 1.

[0110] [Table 1]

[0111]

[0112] *In the compound constituting the nanoparticles, the total content of Ag, Au, chalcogens (Se, S), and In is 100%.

[0113] [Measurement of Absorption Spectra and Luminescence Spectra]

[0114] Next, absorption spectra were measured for each semiconductor nanoparticle of Examples 1 and 2 and Reference Examples 1 and 2. The absorption spectra were measured using an ultraviolet-visible spectrophotometer (Agilent 8453, manufactured by Agilent Technologies) in a wavelength range of 400 nm to 1100 nm.

[0115] In addition, the luminescence spectrum and luminescence quantum efficiency of each nanoparticle were measured. The luminescence spectrum was measured using a diode array spectrophotometer (PMA-12, C10027-02) manufactured by Hamamatsu Photonics KK. The sample was adjusted to an absorbance of 0.1 at 365 nm using a chloroform solution (n = 1.4429).

[0116] In addition, in the measurement of the luminescence quantum yield, the luminescence quantum yield in the wavelength region of 900 nm or less was measured using an absolute PL quantum yield measuring device (C9920-03 manufactured by Hamamatsu Photonics KK). When luminescence was observed at long wavelengths of 1000 nm or longer, the luminescence spectrum was measured using a multi-channel spectrophotometer (PMA-12, manufactured by Hamamatsu Photonics KK (Models: C10027-02 (wavelength range 350-1100 nm) and 10028-01 (wavelength range 900-1650 nm)). The sample was adjusted to an absorbance of 0.1 at 700 nm using a chloroform solution (n = 1.4429). The excitation wavelength was set to 700 nm. To calculate the luminescence quantum yield in the near-infrared region, the luminescence spectrum obtained by fluorescence spectrophotometry was measured against the ethanol solution (n = 1.3618) of indocyanine green (ICG: Φ ​​= 13.2%), a near-infrared luminescent organic fluorescent dye, as a standard sample. The luminescence quantum yield of each sample was calculated using the relative method using the following formula.

[0117] [Mathematical formula 1]

[0118]

[0119] (A: absorbance of the sample at the excitation wavelength, Iex: intensity of the excitation light at the excitation wavelength, n: refractive index of the solvent)

[0120] The absorption spectrum of each semiconductor nanoparticle produced in this embodiment is measured as follows: Figure 2 and Figure 3 In addition, the results of the luminescence spectrum are shown in Figure 4 and Figure 5Table 2 also summarizes the relationship between the emission wavelength and the emission quantum yield of each semiconductor nanoparticle.

[0121] [Table 2]

[0122]

[0123] Reference Figure 3 The absorption edge wavelengths of Examples 1 and 2 (AgAuSeIn) and Reference Example 1 (AgAuSe), in which the chalcogen is Se, are 900 nm or longer. Furthermore, compared to Reference Example 2 (AgAuS), in which the chalcogen is S, the absorption edge wavelengths of these semiconductor nanoparticles are longer. This indicates that using Se as the chalcogen improves photoresponsivity in the long-wavelength region.

[0124] In addition, from Figure 4 It can be seen that the AgAuSeIn nanoparticles of Examples 1 and 2, which are AgAuSe doped with In, are significantly different from the nanoparticles of Reference Example 1 (AgAuSe, Figure 5 ) shows a luminescence peak at approximately the same position (about 980 to 1000 nm), and in addition, compared with Reference Example 2 (AgAuS, Figure 5 The luminescence peak position of the luminescent element (approximately 780 nm) is shown on the longer wavelength side. This result confirms that the use of Se as the essential chalcogen element can address the light response characteristics in the long wavelength region.

[0125] Furthermore, a comparison of Examples 1 and 2 with Reference Example 1 confirms that the doping of In (metal M) into the AgAuS-based compound increases the luminescence quantum efficiency. In particular, the AgAuSeIn nanoparticles of Example 1, synthesized by direct synthesis, exhibit excellent quantum efficiency. The results of this embodiment demonstrate that, in order to form suitable semiconductor nanoparticles, it is preferable to dope In (metal M) with an AgAuSe-based compound containing Se as the essential chalcogen element, thereby achieving excellent luminescence properties in addition to accommodating long-wavelength regions.

[0126] Second embodiment Based on the preferred results of the AgAuSeIn nanoparticles in the first embodiment, in this embodiment, changes in characteristics caused by the amount of In doping in the AgAuSeIn nanoparticles were studied.

[0127] The synthesis of AgAuSeIn nanoparticles in this embodiment is essentially based on Example 1 (direct synthesis) of the first embodiment. Specifically, indium acetate and selenourea, as indium precursors, were placed in a test tube along with 0.075 mmol of silver acetate and 0.025 mmol of gold(I) chloride (dimethylsulfide). 2.9 mL of solvent (oleylamine) and 0.1 mL of protective agent (1-dodecanethiol) were added to synthesize AgAuSeIn nanoparticles. The reaction conditions were a heating temperature of 50°C and a reaction time of 10 minutes. The pre- and post-reaction treatments were the same as in Example 1.

[0128] In this embodiment, the amount of In added in Example 1 (0.1 mmol) was set to "1 times" as a reference, and In was added to the reaction system in amounts of 0.5 times, 0.75 times, 0.88 times, 1.25 times, 1.5 times, 2 times, and 4 times the amount of In added. Furthermore, the amount of Se (selenourea) added was adjusted to achieve an equivalent negative charge based on the amount of In added in each sample, taking into account the positive charges of Ag, Au, and In.

[0129] TEM observation and composition analysis were performed on the AgAuSeIn nanoparticles synthesized at various In doping amounts in the same manner as in the first embodiment. Figure 6 TEM images of AgAuSeIn nanoparticles with various In doping levels (doping levels: 0.5x, 0.75x, 0.88x, 1x, 1.25x, 1.5x, 2x, and 4x). Table 3 also shows the results of composition analysis of these semiconductor nanoparticles.

[0130] [Table 3]

[0131]

[0132] *The In input amount of Example 1 of the first embodiment is set to "1 time".

[0133] *The total content of Ag, Au, Se, and In in the compound constituting the nanoparticles is 100%.

[0134] As can be seen from Table 3, when the amount of In added is changed, the In content of the AgAuSeIn nanoparticles does not differ significantly between 0.5 and 1.25 times the amount of In added. The In content increases significantly when the amount of In added is increased to 1.5 times or more.

[0135] Then, for the AgAuSeIn synthesized in this embodiment, the absorption spectrum, luminescence spectrum and luminescence quantum efficiency were measured using the same method as in the first embodiment of the nanoparticles. The absorption spectrum measurement results of the semiconductor nanoparticles produced in this embodiment (In input amount: 0.5 times, 0.75 times, 0.88 times, 1 times, 1.25 times, 1.5 times, 2 times, 4 times) are as follows: Figure 7 The results of the luminescence spectrum are shown in Figure 8 In addition, the peak wavelength of the luminescence spectrum and the luminescence quantum efficiency are summarized and shown in Table 4.

[0136] [Table 4]

[0137]

[0138] *The In input amount of Example 1 of the first embodiment is set to "1 time".

[0139] Reference Figure 7 The absorption spectrum curves of AgAuSeIn nanoparticles with In additions of 0.5 times and 0.75 times show similar curves, showing a small peak near 850nm, which is believed to be the exciton peak, and an absorption edge near 1040nm. Furthermore, the curves of AgAuSeIn nanoparticles with In additions of 0.88 times and 1 times roughly overlap, showing a small peak near 780nm, which is believed to be the exciton peak, and absorption edges near 850nm and 1000nm. Furthermore, AgAuSeIn nanoparticles with In additions of 1.25 times or more do not show a small peak believed to be the exciton peak, and the absorption edge is near 1040nm.

[0140] Next, refer to Figure 8 The luminescence spectrum measurement results are shown in Table 4. The AgAuSeIn nanoparticles produced in this embodiment exhibit a luminescence peak in the long-wavelength region and a higher quantum yield than the AgAuS nanoparticles of Reference Example 2 of the first embodiment. In particular, AgAuSeIn nanoparticles with an In loading of 0.88 to 1.5 times the In loading exhibited a quantum yield of 40% or higher.

[0141] Furthermore, the peak wavelength of the emission spectrum is categorized by the indium content. AgAuSeIn nanoparticles with 0.5x and 0.75x indium content exhibit a low-intensity peak emission wavelength near 985nm. At 0.88x and 1x indium content, the emission intensity becomes significantly higher, with peak wavelengths observed near 960-980nm. At 1.25x or higher indium content, the peak emission wavelength shifts to a longer wavelength near 1000nm. This is similar to the fact that the shape of the absorption spectrum is categorized by indium content.

[0142] Third embodiment In this embodiment, the ratio of the input amount of the Ag precursor and the Au precursor when synthesizing AgAuSeIn nanoparticles was adjusted to synthesize AgAuSeIn nanoparticles with various compositions, and their properties were studied.

[0143] The synthesis method of AgAuSeIn nanoparticles in this embodiment is essentially based on Example 1 (direct synthesis) of the first embodiment. 0.1 mmol combined of silver acetate and gold(I) chloride (dimethylsulfide), 0.1 mmol of indium acetate, and 0.2 mmol of selenourea were placed in a test tube. 2.9 mL of solvent (oleylamine) and 0.1 mL of protective agent (1-dodecanethiol) were added and heated to synthesize AgAuSeIn nanoparticles.

[0144] In this embodiment, AgAuSeIn nanoparticles were synthesized in such a manner that the ratio (a / (a+b)) of the amount of Ag input relative to the total number of atoms (a) of Ag atoms in the Ag precursor and the total number of atoms (b) of Au atoms in the Au precursor was 0, 0.25, 0.5, 0.75, 0.82, 0.88, 0.94, and 1.0, respectively, with respect to the input amounts of the Ag precursor (silver acetate) and the Au precursor (chloro(dimethylsulfide)gold(I)). In the reaction systems having these input amount ratios, AgAuSeIn nanoparticles were synthesized by setting the heating temperature to 50°C and the reaction time to 20 minutes. In addition, in the reaction systems having the ratio of the amount of Ag input to 0.25, 0.5, 0.75, and 0.88, in addition to the above, AgAuSeIn nanoparticles were synthesized by setting the reaction time to 10 minutes at a heating temperature of 50°C.

[0145] The AgAuSeIn nanoparticles synthesized by adjusting the input ratio of Ag in this embodiment were subjected to TEM observation and composition analysis in the same manner as in the first embodiment. Figure 9a This is a TEM photograph of AgAuSeIn nanoparticles synthesized by setting the Ag input ratio to 0, 0.25, 0.5, 0.75, 0.82, 0.88, 0.94, and 1.0 and heating time to 20 minutes. Figure 9b These are TEM images of AgAuSeIn nanoparticles synthesized at Ag input ratios of 0.25, 0.5, 0.75, and 0.88 and a heating time of 10 minutes. Table 5 shows the results of composition analysis of these semiconductor nanoparticles.

[0146] [Table 5]

[0147]

[0148] *The total content of Ag, Au, Se, and In in the compound constituting the nanoparticles is 100%.

[0149] Table 5 confirms that the Ag content of the AgAuSeIn nanoparticles changes with adjustment of the Ag incorporation ratio. Specifically, the ratio (x / (x+y)) of the number of Ag atoms (x) to the sum of the number of Ag atoms (x) and the number of Au atoms (y) in the AgAuSeIn compound constituting the AgAuSeIn nanoparticles increases with increasing Ag incorporation ratio.

[0150] Next, the absorption spectrum, luminescence spectrum, and luminescence quantum efficiency of each AgAuSeIn nanoparticle were measured. These measurement methods and conditions are essentially the same as those used in the first embodiment. However, for the luminescence spectrum, since the sample with an Ag incorporation ratio of 0.25 has an absorption edge at approximately 700 nm and cannot be excited by excitation light at a wavelength of 700 nm, the excitation wavelength for this sample was set to 365 nm. Figure 10a and Figure 10b The results of measuring the absorption spectrum of the semiconductor nanoparticles produced in this embodiment are shown. Figure 11a and Figure 11b The results of the emission spectrum measurements are shown in Table 6. In addition, the peak wavelength of the emission spectrum and the measured values ​​of the emission quantum efficiency are summarized in Table 6.

[0151] [Table 6]

[0152]

[0153] Reference Figure 10a The absorption spectrum curves of a and b show that the absorption end wavelength tends to become longer as the Ag input ratio increases. Figure 10b For the AgAuSeIn nanoparticles with a reaction time of 10 minutes, the absorption wavelength of the AgAuSeIn nanoparticles with an Ag input ratio of 0.75 is the longest, but when the Ag input ratio is 0.88, the absorption wavelength is slightly shorter. Figure 10a By setting the reaction time to 20 minutes, the absorption end wavelength of the AgAuSeIn nanoparticles with an Ag input ratio of 0.88 is longer than that of the Ag input ratio of 0.75.

[0154] Next, refer to Figure 11aThe measurement results and values ​​of the luminescence spectra in Tables a, b, and 6 show that as the Ag input ratio increases, the luminescence peak tends to shift toward the long wavelength side. Furthermore, the luminescence quantum yield of AgAuSeIn nanoparticles with Ag input ratios of 0.5 and 0.75 is particularly high, and the peak width is also narrowed. No luminescence was observed for nanoparticles with Ag input ratios of 0 and 1.0. It should be noted that, regarding the reaction time, the AgAuSeIn nanoparticles synthesized with a heating time of 20 minutes generally exhibit a luminescence peak on the long wavelength side.

[0155] Figure 12 The XRD analysis results of AgAuSeIn nanoparticles (reaction time 20 minutes and 10 minutes) with Ag input ratios of 0.5 and 0.75 are shown. The XRD analysis device was Smart-Lab-3K manufactured by Rigaku Corporation, the characteristic X-ray was set to CuKα line, and the analysis condition was set to 1° / min. Figure 12 It can be seen that diffraction peaks corresponding to Ag3AuSe2 were observed in all AgAuSeIn nanoparticles synthesized at any Ag incorporation ratio and reaction time. However, the crystallinity of the AgAuSeIn nanoparticles with an Ag incorporation ratio of 0.75 was higher than that of the nanoparticles with an Ag incorporation ratio of 0.5. Furthermore, the peaks of the AgAuSeIn nanoparticles with an Ag incorporation ratio of 0.75 became sharper when the reaction time was set to 20 minutes, indicating further improvement in crystallinity.

[0156] Fourth embodiment In this embodiment, AgAuSeIn nanoparticles were synthesized at various reaction times to further investigate the reaction time. In this embodiment, the reaction system was configured under the same conditions as in Example 1 of the first embodiment (Ag input ratio: 0.75, In input amount: 1). The AgAuSeIn nanoparticles were synthesized at a reaction temperature of 50°C and reaction times of 5 minutes, 10 minutes, 15 minutes, 20 minutes, 40 minutes, and 80 minutes.

[0157] The AgAuSeIn nanoparticles synthesized by adjusting the reaction time in this embodiment were subjected to TEM observation and composition analysis. Figure 13 TEM images of various AgAuSeIn nanoparticles (reaction time: 5 minutes, 10 minutes, 15 minutes, 20 minutes, 40 minutes, and 80 minutes) are shown in Table 7. The results of the composition analysis of these semiconductor nanoparticles are also shown.

[0158] [Table 7]

[0159]

[0160] *The total content of Ag, Au, Se, and In in the compound constituting the nanoparticles is 100%.

[0161] As shown in Table 7, the Ag content tends to decrease and the Se content to increase with increasing reaction time. However, these changes are slight and not drastic. It is believed that increasing reaction time does not significantly affect the composition of the AgAuSeIn nanoparticles.

[0162] Therefore, the absorption spectrum, luminescence spectrum, and luminescence quantum efficiency of each AgAuSeIn nanoparticle were measured. These measurement methods and conditions are basically the same as those in the first embodiment. Figure 14 The results of measuring the absorption spectra of the semiconductor nanoparticles produced in this embodiment (reaction time: 5 minutes, 10 minutes, 15 minutes, 20 minutes, 40 minutes, and 80 minutes) are shown. Figure 15 The results of the emission spectrum measurements are shown in Table 8. In addition, the peak wavelength of the emission spectrum and the emission quantum efficiency are summarized in Table 8.

[0163] [Table 8]

[0164]

[0165] Reference Figure 14 From the absorption spectrum curve, we can see that as the reaction time increases, the absorption end tends to shift to the long wavelength side. Figure 14 Looking at the enlarged image, the absorption spectra for reaction times of 5 and 10 minutes shift slightly, but the shapes are similar, confirming two absorption edges. The shape of the absorption spectrum changes significantly when the reaction time exceeds 15 minutes, but then becomes roughly the same.

[0166] Reference Figure 15 The luminescence spectrum measurements shown in Table 8 show that the AgAuSeIn nanoparticles synthesized in this embodiment while adjusting the reaction time all exhibited high luminescence quantum yields of 40% or higher. However, based on the peak luminescence wavelength, they can be grouped into two categories: those with a reaction time of 10 minutes or less, which exhibited a peak at wavelengths below 1000 nm, and those with a reaction time of 15 minutes or longer, which exhibited a peak at wavelengths above 1000 nm.

[0167] Figure 16The XRD analysis results of AgAuSeIn nanoparticles synthesized with reaction times of 10 minutes, 20 minutes and 80 minutes are shown. As described in the research results of the third embodiment, by setting the reaction time to 20 minutes, the diffraction peak becomes sharp and it can be seen that the crystallinity improves. However, the crystallinity caused by the increase in the reaction time changes very little even after an excessively long time. This is because there is almost no difference between the diffraction peak with a reaction time of 80 minutes and the diffraction peak with a reaction time of 20 minutes. When considering grouping based on the measurement results of the luminescence peak wavelength in Table 8, it can be predicted that in the stage with a reaction time of 10 minutes to 15 minutes, some structural changes have occurred in the AgAuSeIn nanoparticles. This structural change is not limited to simple crystallization, and it is envisaged that the changes in the element distribution in the particles such as the nanoparticles becoming core-shell structures are also included, but the details are still uncertain.

[0168] Industrial Applicability

[0169] As described above, the novel semiconductor nanoparticles composed of the AgAuSe-based polynary compound of the present invention can exhibit excellent optical semiconductor properties. Furthermore, the AgAuSe-based polynary compound is a biocompatible, low-toxic compound. Thus, the semiconductor nanoparticles of the present invention are expected to be applied to light-emitting elements, fluorescent materials used in display devices or markers for detecting bio-related substances, or to photoelectric conversion elements or light-receiving elements mounted on solar cells or light sensors.

[0170] The semiconductor nanoparticles of the present invention achieve improved light emission and absorption properties in the long-wavelength region of the near-infrared (NIR) or short-wave infrared (SWIR) regions. Therefore, the present invention is particularly useful for light-receiving elements used in LIDAR and SWIR image sensors, which prioritize responsiveness in the near-infrared region.

Claims

1. A semiconductor nanoparticle composed of a compound containing Ag, Au, a chalcogen element having Se as an essential component, and a metal M as an essential constituent element, The metal M is at least one of Al, Ga, In, Tl, Zn, Cd, Hg, and Cu, In the compound, the total content of Ag, Au, a chalcogen element including Se as an essential element, and the metal M is 95% by mass or more.

2. The semiconductor nanoparticle according to claim 1, wherein The content of the metal M in the compound is 1 atomic % or more and 50 atomic % or less.

3. The semiconductor nanoparticle according to claim 1 or claim 2, wherein In the compound, a ratio of the number x of Ag atoms to the total number x of Ag atoms and the number y of Au atoms (x / (x+y)) is 0.20 or more and 0.95 or less.

4. The semiconductor nanoparticle according to claim 1 or claim 2, wherein The content of the essential chalcogen element, Se, in the compound is not less than 25 atomic % and not more than 60 atomic %.

5. The semiconductor nanoparticle according to claim 3, wherein The content of the essential chalcogen element, Se, in the compound is not less than 25 atomic % and not more than 60 atomic %.

6. The semiconductor nanoparticle according to claim 1 or claim 2, wherein The compound is obtained by doping a compound containing Ag, Au, and Se with a metal M.

7. The semiconductor nanoparticle according to claim 1 or claim 2, wherein The compound is composed of: a core compound containing Ag, Au, and Se; and a shell compound covering at least a portion of the surface of the core compound, wherein the shell compound is a metal M and / or necessarily contains a metal M and contains at least any one of Ag, Au, and Se.

8. The semiconductor nanoparticle according to claim 1 or claim 2, wherein The average particle size is 2 nm or more and 20 nm or less.

9. The semiconductor nanoparticle according to claim 1 or claim 2, At least one of an alkylamine having an alkyl chain with 4 to 20 carbon atoms, an alkenylamine having an alkenyl chain with 4 to 20 carbon atoms, an alkylcarboxylic acid having an alkyl chain with 3 to 20 carbon atoms, an alkenylcarboxylic acid having an alkenyl chain with 3 to 20 carbon atoms, an alkanethiol having an alkyl chain with 4 to 20 carbon atoms, a trialkylphosphine having an alkyl chain with 4 to 20 carbon atoms, a trialkylphosphine oxide having an alkyl chain with 4 to 20 carbon atoms, triphenylphosphine, and triphenylphosphine oxide is bound to its surface as a protecting agent.

10. The semiconductor nanoparticle according to claim 1 or claim 2, wherein The long-wavelength absorption end wavelength of the absorption spectrum is 800 nm or longer.

Images