Semiconductor nanoparticles mainly composed of AgAuTeS compounds

Abstract

Disclosed is a semiconductor nanoparticle composed of a metal chalcogenide, which has improved particle size uniformity and morphological stability and exhibits photoresponsiveness in a longer wavelength region than conventional products. SOLUTION: The present invention provides a semiconductor nanoparticle comprising an AgAuTeS compound represented by the following formula consisting of Ag, Au, Te, and S. In the following formula, x is the atomic ratio of Ag, satisfying 0.50 ≦ x ≦ 0.65; y is the atomic ratio of Au, satisfying 0.01 ≦ y ≦ 0.10; z is the total atomic ratio of Te and S as chalcogen elements, satisfying 0.25 ≦ z ≦ 0.50; and a is the atomic ratio of S in the chalcogen elements, satisfying 0 < a < 1. Compared with conventional AgAuTe compound nanoparticles, the present invention achieves improvement in particle size distribution and the like by compounding Te and S as chalcogen elements. TIFF0007913715000014.tif13137

Description

[Technical Field]

[0001] The present invention relates to semiconductor nanoparticles mainly composed of an AgAuTeS compound, which consists of metallic elements Ag and Au and chalcogen elements Te and S. More specifically, the present invention relates to semiconductor nanoparticles of the AgAuTeS compound that have good particle size uniformity and suitable light absorption and emission properties. [Background technology]

[0002] Semiconductor nanoparticles known as quantum dots (QDs) have recently attracted attention for their potential applications in various technological fields. For example, they are being considered for use as photoelectric conversion elements in solar cells, light-receiving elements in photosensors and other light-emitting elements in display devices, and as fluorescent materials used as markers for detecting bio-related substances. Quantum dots are functional materials that utilize the quantum confinement effect of semiconductors, and by adjusting the band gap through particle size and composition, the photoresponse properties of absorption and emission wavelengths can be suitably set.

[0003] The applications of semiconductor nanoparticles as quantum dots have so far included light-absorbing layers in solar cells, where the corresponding wavelength range is in the visible light region. However, as mentioned above, semiconductor nanoparticles can exhibit flexible photoresponse, so they are expected to be used in applications where photoresponse can be exhibited in the near-infrared (NIR) and short-wave infrared (SWIR) regions, which are longer wavelengths than the visible light region. Fields where the use of semiconductor nanoparticles is expected in the future include, for example, photodetectors in LIDAR (Light Detection and Ranging) and SWIR image sensors used in the control of autonomous vehicles and drones. In these applications, it is necessary to have a response in the long-wavelength range that is less affected by sunlight and natural light.

[0004] As described above, there are several reports, including those by the present applicant, on the development of semiconductor nanoparticles that prioritize photoresponsiveness in the long-wavelength region. The present applicant has reported on the nanoparticle formation of compound semiconductors of various compositions, such as AgAuS compounds (Patent Document 1), AgAuSe compounds (Patent Document 2), and AgAuTe compounds (Patent Document 3), and their photoresponsiveness characteristics. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 7269591 Specification [Patent Document 2] Patent No. 7580090 specification [Patent Document 3] Patent No. 7521746 specification [Overview of the project] [Problems that the invention aims to solve]

[0006] The semiconductor nanoparticles developed by the applicants described above are compounds (metallic chalcogenides) of transition metals such as Ag and Au with one of the chalcogen elements, S, Se, or Te. These semiconductor nanoparticles made of metallic chalcogenides have photoresponsiveness in the near-infrared region and are therefore suitable for the applications described above. Furthermore, these metallic chalcogenide nanoparticles all have low toxicity and low environmental impact, making them useful in reducing costs and safety risks from manufacturing to use. In particular, the semiconductor nanoparticles made of the AgAuTe compound described in Patent Document 3 have an absorption edge wavelength of 1200 nm or more in their absorption spectrum, and can respond to light in a longer wavelength region than AgAuS and AgAuSe.

[0007] As described above, research on quantum dot technology related to semiconductor nanoparticles has progressed considerably compared to the initial stage, and the basic constitution of semiconductor compounds that can be expected to be useful is gradually being clarified. However, according to studies conducted by the applicant of the present application and others, the above-mentioned semiconductor nanoparticles still have problems to be overcome. For example, among the semiconductor nanoparticles developed by the applicant of the present application and others in Patent Documents 1 to 3, the semiconductor nanoparticles composed of an AgAuTe compound (Patent Document 3), which is regarded as particularly useful in terms of the corresponding wavelength range, has inferior particle size uniformity and particle morphology stability. When forming a light-receiving element for LIDAR or the like, semiconductor nanoparticles are laminated to form a thin film, but it is difficult to obtain a uniform and suitable thin film with particles of non-uniform shape and particle size. Further, according to Patent Document 3, although semiconductor nanoparticles composed of an AgAuTe compound have good light absorption properties, their light emission properties have not been confirmed. Some applications of semiconductor nanoparticles require light-emitting properties, so it must be said that materials for which this point is unclear are somewhat lacking in practicality.

[0008] For application to LIDAR and other fields, studies on improving the photoresponsiveness of semiconductor nanoparticles should be continued in the future, and semiconductor nanoparticles capable of exhibiting absorption and emission properties in longer wavelength ranges than ever before are needed.

[0009] The present invention has been made against the above background. In connection with the above conventional semiconductor nanoparticles made of metal chalcogenide, the present invention solves specific problems such as particle size uniformity and morphological stability, and provides a material that can exhibit photoresponsiveness in a longer wavelength region than ever before. [Means for Solving the Problems]

[0010] The present inventors have focused on semiconductor nanoparticles composed of AgAuTe compounds, which maximize the adaptable wavelength range among the aforementioned semiconductor nanoparticles composed of metal chalcogenides, and have studied improvements thereto. The photoresponse characteristics of metal chalcogenides correlate with the mass (atomic weight) of the chalcogen element. It is presumed that the reduction in the orbital energy difference between the metal element and the chalcogen element caused by an increase in the mass of the chalcogen element shifts the photoresponse of the compound to the longer wavelength side. Te has a larger mass than S and Se, and this effect can be effectively utilized, thus highlighting the usefulness of AgAuTe compounds. However, as described above, AgAuTe compounds have problems such as non-uniform particle size when formed into nanoparticles. The present inventors have studied methods for forming suitable nanoparticles while utilizing the advantages of AgAuTe compounds, and as a result, have arrived at the concept of compounding chalcogen elements that bind to metal components (Ag and Au). Specifically, the inventors have found that uniform particle size distribution of nanoparticles can be imparted by using a combination of Te and S as the chalcogen elements.

[0011] The method of adding S to an AgAuTe compound to improve particle size distribution involves adding a low-mass chalcogen element to a high-mass chalcogen element, so at first glance it appears to partially eliminate the aforementioned effects obtained by using Te. However, if compounding chalcogen elements can stabilize the particle size and morphology of semiconductor nanoparticles while refining them, the advantage of strengthening the quantum confinement effect and leading to improved photoresponse can be expected. The present inventors have studied the method for synthesizing nanoparticles of AgAuTeS compounds and the characteristics of the synthesized semiconductor nanoparticles based on this approach. As a result, the inventors have found that by setting the atomic ratio of each constituent element within a predetermined range, the material can exhibit suitable light absorption properties as well as light-emitting characteristics, and thus arrived at the present invention.

[0012] That is, the present invention provides semiconductor nanoparticles comprising an AgAuTeS compound represented by the following formula, consisting of Ag, Au, Te and S.

[0013]

Chemical Formula

[0014] The following describes the AgAuTeS compound, which is the main component of the semiconductor nanoparticles according to the present invention, its synthesis method, and the uses of the semiconductor nanoparticles according to the present invention.

[0015] A. Structure of semiconductor nanoparticles according to the present invention A-1. Chemical composition of semiconductor nanoparticles As described above, the semiconductor nanoparticles according to the present invention are metal chalcogenides (Ag) composed of the metal elements Ag and Au and the chalcogen elements Te and S. x Au y (Te 1-a S a ) z The semiconductor nanoparticles of this invention are mainly composed of ). The semiconductor nanoparticles of this invention exhibit suitable photoresponse characteristics depending on the atomic ratios of each constituent element, which are x, y, z, and a.

[0016] For the atomic ratios of Ag and Au, which are the metal components of the metal chalcogenide (AgAuTeS compound) applied to the present invention, x is set to 0.50 ≤ x ≤ 0.65 and y is set to 0.01 ≤ y ≤ 0.1. The atomic ratio of the metal components affects the luminescence properties of the semiconductor nanoparticles, and by setting both x and y within the above ranges, the semiconductor nanoparticles become luminescent. The preferred ranges for x and y are 0.55 ≤ x ≤ 0.65 and 0.01 ≤ y ≤ 0.05. Furthermore, the atomic ratio of Ag in the metal component, x / (x+y), is preferably 0.9 ≤ x / (x+y) < 1.0, and more preferably 0.920 ≤ x / (x+y) < 0.999.

[0017] On the other hand, regarding the chalcogen component (chalcogen element), in the present invention, the chalcogen component is composed of Te and S. Compared with the conventional AgAuTe compound, forming the chalcogen component from two types of chalcogen elements can uniformize and stabilize the particle size and morphology when the semiconductor nanoparticles are produced. Although the reason for this is not clear, the present inventors presume that it is because the solid solution of S into the AgAuTe compound crystal slows down the crystal growth rate. The atomic ratio a of S in the chalcogen elements (Te and S) of the AgAuTeS compound is adjusted within the range of 0 < a < 1. The atomic ratio a of S in the chalcogen elements can affect the particle size distribution of the semiconductor nanoparticles. Deterioration of the particle size distribution of the semiconductor nanoparticles can cause not only the loss of luminescence properties but also the degradation of absorption properties. The range of the atomic ratio a of S in the chalcogen elements is preferably 0.1 ≤ a ≤ 0.5, more preferably 0.25 ≤ a ≤ 0.45.

[0018] In the metal chalcogenide (AgAuTeS compound) applied to the present invention, the chalcogen components Te and S are bonded such that charge compensation is achieved for the metal components Ag and Au. In the semiconductor nanoparticles of the present invention, it is preferable that z / (x+y), which is the atomic ratio of the total chalcogen component to the total metal component, satisfies 1.5 ≦ z / (x+y) ≦ 2.0.

[0019] The composition of the AgAuTeS compound described above refers to the overall composition of the AgAuTeS compound contained in the semiconductor nanoparticles. The AgAuTeS compound applied to the present invention may be composed only of an alloy phase with a single composition, or may be composed of alloy phases with a plurality of compositions. It is only required that x, y, and z are within the above-mentioned ranges for the entire AgAuTeS compound in the semiconductor nanoparticles. The composition of the AgAuTeS compound can be obtained by performing composition analysis on multiple locations of the semiconductor nanoparticles and calculating the average value.

[0020] The semiconductor nanoparticles according to the present invention are AgAuTeS compounds having the composition range described above (Ag x Au y (Te 1-a S a )z The semiconductor nanoparticles according to the present invention may consist solely of the AgAuTeS compound, and this form is preferred. However, the semiconductor nanoparticles according to the present invention may contain elements other than Ag, Au, Te, and S, which constitute the AgAuTeS compound. For example, constituent elements of the solvent used when synthesizing the semiconductor nanoparticles, or elements in the raw materials (precursors) of Ag, Au, Te, and S may be contained in the semiconductor nanoparticles. Elements other than these essential constituent elements that may be contained in semiconductor nanoparticles include C, P, Cl, Br, I, etc. When considering the presence of these other elements, the semiconductor nanoparticles according to the present invention preferably contain 90 atomic% or more of the AgAuTeS compound described above, and more preferably contain 95 atomic% or more. Note that this AgAuTeS compound content is a numerical range for semiconductor nanoparticles and does not include the content of the protective agent and constituent elements of the protective agent described later.

[0021] The particle size of the semiconductor nanoparticles according to the present invention is preferably such that the average particle size is 1 nm or more and 20 nm or less, more preferably 1 nm or more and 10 nm or less, and even more preferably 1 nm or more and 5 nm or less. The particle size of the semiconductor nanoparticles is related to the adjustment effect of the band gap due to the quantum confinement effect. Since the photoresponse characteristics also change with changes in the band gap, the above average particle size is preferable. Furthermore, the particle size distribution is an indicator that should be considered in order for the semiconductor nanoparticle group to exhibit uniform and suitable photoresponse. In the present invention, it is preferable that the standard deviation σ of the particle size distribution of the semiconductor nanoparticles is 1.0 nm or less. The average particle size and standard deviation of semiconductor nanoparticles can be obtained by observing a plurality of semiconductor nanoparticles (preferably 100 or more) with an electron microscope such as a TEM, measuring the particle size of each particle, etc., and calculating the average particle number.

[0022] Furthermore, the semiconductor nanoparticles according to the present invention can take on shapes other than spherical, such as cube or rod shapes. In this case, the particle size of the semiconductor nanoparticles can be measured as the diameter in the case of spherical shapes, and as the average value of the major axis and minor axis in the case of cube or rod shapes. However, in the present invention, it is preferable that the nanoparticles be spherical or have a shape that can approximate a spherical shape.

[0023] Furthermore, scanning transmission electron microscopy (STEM) is suitably used for analyzing the composition, particle size, and structure of semiconductor nanoparticles as described above. In particular, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) allows for obtaining scattering images that reflect the compositional information of the nanoparticles, and when combined with energy-dispersive X-ray spectrometers (EDS, EDX), the distribution of Ag, Au, Te, and S, as well as the overall composition of the nanoparticles, can be determined.

[0024] A-2. Semiconductor properties of semiconductor nanoparticles according to the present invention The photoresponsiveness of semiconductor nanoparticles changes as their band gap is adjusted by a quantum confinement effect depending on their particle size. The semiconductor nanoparticles according to the present invention also have photoresponsiveness through a similar mechanism. Regarding the photoabsorption characteristics of the semiconductor nanoparticles according to the present invention, it is preferable that the absorption edge wavelength on the long-wavelength side of the absorption spectrum is 1200 nm or higher. This allows the semiconductor nanoparticles to exhibit absorption for light from the visible light region to the near-infrared region. In a more preferable embodiment, the semiconductor nanoparticles according to the present invention can have an absorption edge wavelength on the long-wavelength side of 1300 nm or higher. Furthermore, an exciton peak may be observed in the absorption spectrum of the semiconductor nanoparticles according to the present invention. The exciton peak is an absorption peak that appears due to the generation of excitons. The appearance of the exciton peak in the absorption spectrum is due to the semiconductor nanoparticles having good uniformity, few defects, and crystalline properties.

[0025] Furthermore, the semiconductor nanoparticles according to the present invention can also exhibit a light emission phenomenon. In this case, a preferred embodiment of the peak wavelength of the emission spectrum is that, according to the semiconductor nanoparticles according to the present invention, an emission peak can be shown in the long wavelength region of 1000 nm or more, more preferably 1200 nm or more.

[0026] A-3. Utilization of semiconductor nanoparticles according to the present invention The semiconductor nanoparticles according to the present invention can be applied to various uses such as photodetectors and light-emitting elements by coating or supporting them on a suitable substrate or support. There are no particular restrictions on the composition, shape, or dimensions of the substrate or support. Examples of substrates in the form of plates, foils, or films include glass, quartz, silicon, ceramics, or metals. Examples of granular or powdery supports include particles or powders of inorganic oxides such as ZnO, TiO2, WO3, SnO2, In2O3, and Al2O3. The semiconductor nanoparticles may be supported on the inorganic oxide support and then fixed to another substrate.

[0027] Furthermore, when coating or supporting semiconductor nanoparticles on a substrate or support, as described above, solutions, slurries, or inks in which semiconductor nanoparticles are dispersed in an appropriate dispersion medium are often used. Suitable dispersion media for these solutions include chloroform, toluene, cyclohexane, and hexane. Various methods can be used for coating the semiconductor nanoparticle solution, such as dipping and spin coating, and for supporting the nanoparticles, such as dropping, impregnation, and adsorption.

[0028] Furthermore, the semiconductor nanoparticles according to the present invention may contain a protective agent to suppress aggregation of the semiconductor nanoparticles during their synthesis process and when dispersed in a dispersion medium as described above. The details of the action and composition of the protective agent will be described later. The protective agent binds to the surface of the semiconductor nanoparticles and coats at least a portion of them, suppressing aggregation of the semiconductor nanoparticles in the dispersion liquid and resulting in a homogeneous solution. In addition, in the semiconductor nanoparticle synthesis process, by adding the protective agent together with the raw materials to the reaction system, nanoparticles with a suitable average particle size can be synthesized. Although excess amounts of the protective agent added during the semiconductor nanoparticle synthesis process are removed by post-synthesis washing and other treatments, some may remain and bind to the surface of the semiconductor nanoparticles.

[0029] B. Method for synthesizing semiconductor nanoparticles according to the present invention Next, the method for synthesizing semiconductor nanoparticles according to the present invention will be described. The main component of the semiconductor nanoparticles of the present invention is the AgAuTeS compound (Ag x Au y (Te 1-a S a ) z As a method for synthesizing AgAuTeS while simultaneously forming nanoparticles, it is preferable to prepare precursors of each constituent element (Ag precursor, Au precursor, Te precursor, S precursor), and simultaneously mix the metal components (Ag precursor, Au precursor) and chalcogen components (S precursor, Te precursor) together to proceed with the synthesis reaction and nanoparticle formation. By reacting the precursors of each element simultaneously, decomposition of each precursor and interaction of the constituent elements released by the decomposition occur, resulting in the synthesis of the AgAuTeS compound. By applying this synthesis method, it is thought that Te and S bond in a suitable ratio to form the compound skeleton, and the metal components react to this skeleton to form highly crystalline AgAuTeS compound nanoparticles. The following describes the method for synthesizing semiconductor nanoparticles of AgAuTeS compound according to the present invention.

[0030] B-1. Metallic and chalcogen components As described above, in the synthesis of semiconductor nanoparticles according to the present invention, it is preferable to mix the metal component and the chalcogen component simultaneously and all at once. In this case, the metal component may be a mixture of Ag precursor and Au precursor, or they may be prepared separately. Similarly, the chalcogen component may be a mixture of S precursor and Te precursor, or they may be prepared separately. Here, "precursor" refers to the raw materials corresponding to each constituent element (Ag, Au, Te, S) of the AgAuTeS compound, and is a complex or compound of each constituent element.

[0031] Regarding the Ag and Au precursors that constitute the metal components, the Ag precursor is preferably an Ag salt or Ag complex containing monovalent Ag. Suitable specific examples of Ag precursors include silver acetate (Ag(OAc)), silver nitrate, silver carbonate, silver oxide, silver oxalate, silver chloride, silver iodide, silver(I) cyanide salt, and silver diethyldithiocarbamate. As for the Au precursor, an Au salt or Au complex containing monovalent or trivalent Au is preferred, and a monovalent Au salt or Au complex is more preferred. Trivalent Au salts or complexes can also be used because, during the synthesis process of the compound, the trivalent Au is reduced to monovalent Au by the solvent or coexisting Te precursors. Suitable specific examples of Au precursors include chloro(dimethyl sulfide) gold(I) ((CH3)2SAuCl) and Au resinate (C 10 H 18 Examples include Au2S2 (CAS 68990-27-2), gold(I) iodide, gold(I) sulfite, chlorauric acid(III), gold(III) acetate, gold(I) cyanide, gold(III) cyanide, 1,10-phenanthroline gold(III), etc.

[0032] As described above, the metal components may be a mixture of Ag precursors and Au precursors, or they may be prepared separately. It is sufficient that the Ag precursors and Au precursors are mixed during the semiconductor nanoparticle synthesis stage, i.e., when they are mixed with the chalcogen component. In either case, it is preferable that the Ag precursors and Au precursors be dissolved in a solvent. Suitable solvents include octadecene, tetradecane, oleic acid, oleylamine, or mixtures thereof.

[0033] For the Te precursor and S precursor, which are chalcogen components, elemental tellurium and tellurium compounds can be used as Te precursors. Examples of Te compounds include oxides and hydroxides, and specifically, tellurium compounds such as tellurium oxide (TeO2), telluric acid (Te(OH)6), and sodium tellurite (Na2TeO3) can be used. Furthermore, elemental sulfur and sulfur compounds can be used as S precursors. Examples of sulfur compounds include thiols, dithiols, thiourea, and alkylthiourea. When thiols are used as sulfur compounds that serve as S precursors, they can also act as solvents and / or protective agents, as described later.

[0034] The chalcogen components, the S precursor and Te precursor, may be mixed together or prepared separately. Furthermore, it is preferable that the S precursor and Te precursor are dissolved in the solvent. In addition to the solvents used for the metal components mentioned above, thiols such as dodecanethiol can be used as the solvent.

[0035] The AgAuTeS compound (Ag) synthesized in this invention x Au y (Te 1-a S a ) z The composition (x, y, z, a) of each constituent element can be adjusted by the amount of each elemental precursor mixed (amount added). For example, to bring the atomic ratios x and y of the metal components Ag and Au within the above-mentioned range, it is preferable to set 0.5 ≤ X / (X+Y) ≤ 0.75, where X is the number of Ag atoms (moles) derived from the Ag precursor and Y is the number of Au atoms (moles) derived from the Au precursor. Furthermore, to synthesize the AgAuTeS compound while compounding the chalcogen components Te and S, it is preferable to have an excess of S atoms derived from the S precursor compared to the number of Te atoms derived from the Te precursor.

[0036] Furthermore, when synthesizing semiconductor nanoparticles according to the present invention, it is preferable to add a protective agent to the reaction system. The protective agent is added to bind to the surface of the AgAuTeS compound nanoparticles produced by the synthesis reaction and suppress the aggregation of the nanoparticles. At least one of the following is preferred as the protective agent: thiols having 4 to 20 carbon atoms, sulfides having 4 to 20 carbon atoms, thioesters having 4 to 20 carbon atoms, or thioketones having 4 to 20 carbon atoms. More preferred protective agents are thiols having 4 to 20 carbon atoms having alkyl groups, sulfanyl groups, etc., as substituents, specifically dodecanethiol, octanthiol, decanethiol, undecanethiol, and nonanthiol. These protective agents can be applied individually or in combination.

[0037] One method for adding a protective agent to the reaction system for synthesizing semiconductor nanoparticles is to add it to at least one of the Ag, Au, Te, or S precursors before synthesis. Due to the function of the protective agent, it is sufficient for it to be present in the reaction system when the semiconductor nanoparticles are formed; therefore, it is not necessary to add the protective agent to all precursors. Furthermore, as mentioned above, thiols such as dodecanethiol have both solvent and protective properties for each precursor. In particular, since thiols can dissolve Te precursors such as tellurium oxide, applying thiols as a solvent for the Te precursor or the entire reaction system allows them to act as protective agents for semiconductor nanoparticles.

[0038] B-2. Synthesis reaction of semiconductor nanoparticles (AgAuTeS compounds) By mixing the above-mentioned Ag precursor, Au precursor, Te precursor, and S precursor together, the AgAuTeS compound (Ag) which constitutes semiconductor nanoparticles is formed. x Au y (Te 1-a S a ) z A reaction system is formed. Then, by reacting this reaction system under appropriate reaction conditions, semiconductor nanoparticles according to the present invention are synthesized.

[0039] The semiconductor nanoparticles according to the present invention are synthesized by heating the reaction system. The heating temperature (reaction temperature) at this time is set to room temperature or higher and 100°C or lower. Below room temperature, the synthesis reaction of the AgAuTeS compound is difficult to carry out. On the other hand, at reaction temperatures exceeding 100°C, there is a risk of a decrease in the uniformity of the particle size and loss of shape stability of the synthesized AgAuTeS compound particles. As a general trend, the average particle size of the synthesized semiconductor nanoparticles increases with increasing reaction temperature. A more preferable reaction temperature is 60°C or higher and 80°C or lower.

[0040] Furthermore, the reaction time (heating time) can be adjusted depending on the amount of raw materials used, but it is preferable to set it to 5 minutes or more and 100 minutes or less. More preferably, the reaction time should be 10 minutes or more, and even more preferably 15 minutes or more. It is also preferable to stir the reaction system in order to allow the synthesis reaction of the AgAuTeS compound to proceed.

[0041] The AgAuTeS compound after the synthesis reaction can be recovered as semiconductor nanoparticles after cooling the reaction system as needed. At this time, the nanoparticles can be precipitated by adding a poor solvent such as alcohol (ethanol, methanol, etc.), or by centrifugation, and then the particles can be washed with alcohol (ethanol, methanol, etc.) and uniformly dispersed in a good solvent such as chloroform. [Effects of the Invention]

[0042] As described above, the present invention relates to semiconductor nanoparticles mainly composed of a metal chalcogenide, and the semiconductor nanoparticles are composed of an AgAuTeS compound in which the chalcogen element is a combination of Te and S. The semiconductor nanoparticles according to the present invention have good particle size uniformity and a well-formed shape. The semiconductor nanoparticles according to the present invention have good light absorption characteristics in the long wavelength region and also have luminescence characteristics, achieved by applying an AgAuTeS compound of a predetermined composition and a suitable particle size distribution. [Brief explanation of the drawing]

[0043] [Figure 1]TEM images of AgAuTeS compound nanoparticles synthesized by varying the reaction temperature in the first embodiment. [Figure 2] A graph showing the particle size distribution of AgAuTeS compound nanoparticles synthesized by varying the reaction temperature in the first embodiment. [Figure 3] XRD diffraction patterns of AgAuTeS compound nanoparticles synthesized by varying the reaction temperature in the first embodiment. [Figure 4] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the first embodiment. [Figure 5] TEM images of AgAuTeS compound nanoparticles synthesized by varying the reaction time in the second embodiment. [Figure 6] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the second embodiment. [Figure 7] TEM image of AgAuTeS compound nanoparticles synthesized in the third embodiment by changing the reaction time to 60 minutes and the reaction temperature. [Figure 8] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the third embodiment. [Figure 9] TEM image of AgAuTeS compound nanoparticles synthesized in the fourth embodiment using AgCl as the Ag precursor and HAuCl4 as the Au precursor. [Figure 10] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the fourth embodiment using AgCl as the Ag precursor. [Figure 11] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the fourth embodiment using HAuCl4 as the Au precursor. [Figure 12] TEM images of AgAuTeS compound nanoparticles synthesized by changing the Ag charging ratio in the fifth embodiment. [Figure 13] (a) Absorption spectrum and (b) Emission spectrum of AgAuTeS compound nanoparticles synthesized in the fifth embodiment. [Modes for carrying out the invention]

[0044] First Embodiment The embodiments of the present invention will be described below. In this embodiment, the AgAuTeS compound (Ag) is prepared using the Ag precursor, Au precursor, Te precursor, and S precursor exemplified above, while adjusting the reaction temperature. x Au y (Te 1-a S a ) z Semiconductor nanoparticles consisting of ) were synthesized. Then, the particle size and particle size distribution of the synthesized semiconductor nanoparticles were measured by visual observation, and their light absorption and emission properties were evaluated.

[0045] [Synthesis of semiconductor nanoparticles] In this embodiment, semiconductor nanoparticles of the AgAuTeS compound (AgAuTeS compound nanoparticles) were synthesized by mixing and heating Ag precursors, Au precursors, and Te precursors with an S precursor that also serves as a solvent and protective agent. 0.3 mmol of silver acetate (Ag(OAc)) as the Ag precursor and 0.1 mmol of chloro(dimethyl sulfide) gold ((CH3)2SAuCl) as the Au precursor were weighed and placed in test tubes. Then, under a nitrogen atmosphere, 0.2 mmol of tellurium oxide (TeO2) as the Te precursor was weighed into the same test tube. After adding a stirring bar to this test tube, the S precursor and 0.15 cm³ of 1-dodecanethiol (DDT), which serves as a solvent and protective agent, were added. 3 And, 0.15 cm of dehydrated oleinamine (OLA) which is the solvent. 3 The following was added. Then, the mixture was heated with stirring at the set reaction temperatures (80°C, 100°C, 120°C, 135°C, 150°C) for 15 minutes to synthesize AgAuTeS compound nanoparticles. After the reaction was complete, the mixture was allowed to cool for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to separate the supernatant from the precipitate. Then, ethanol was added to the supernatant as a poor solvent in a 4 cm solution. 3 In addition, a precipitate was formed, and the precipitate was centrifuged at 4000 rpm for 5 minutes to collect the AgAuTeS compound nanoparticles.

[0046] [TEM observation of AgAuTeS compound nanoparticles] TEM observation was performed on semiconductor nanoparticles made of the AgAuTeS compound synthesized in this embodiment. Figure 1 shows TEM images of AgAuTeS compound nanoparticles synthesized at reaction temperatures of 80°C, 100°C, 120°C, 135°C, and 150°C. Referring to Figure 1, the AgAuTeS compound nanoparticles synthesized at reaction temperatures of 80°C, 100°C, 120°C, and 135°C were spherical or ellipsoidal particles, but the AgAuTeS compound nanoparticles synthesized at a reaction temperature of 150°C underwent aggregation and became amorphous particles.

[0047] Based on these TEM images, the particle sizes of 100 or more particles were measured using image processing software (ImageJ, manufactured by the National Institutes of Health (NIH)) to calculate the average particle size, standard deviation σ, and particle size distribution (based on particle number). Figure 2 shows the particle size distribution, average particle size, and standard deviation of AgAuTeS compound nanoparticles synthesized at each reaction temperature except 150°C. Average particle size and particle size distribution measurements were not performed for the 150°C result because individual particles could not be distinguished from the aggregate. From Figures 1 and 2, it can be seen that as the reaction temperature increases, the average particle size of AgAuTeS compound nanoparticles increases, and the particle size distribution shifts to larger particle sizes. The standard deviation σ of the particle size also increases with increasing reaction temperature. Considering the TEM observation results of particle shape and particle size measurement results in this embodiment, it is considered preferable to keep the reaction temperature below 100°C in order to optimize the morphology, particle size, and particle size distribution of semiconductor nanoparticles.

[0048] [Compositional analysis and XRD analysis of AgAuTeS compound nanoparticles] The compositional analysis of the AgAuTeS compound nanoparticles synthesized in this embodiment was performed by EDX analysis. The results are shown in Table 1. In this embodiment and the subsequent second to fifth embodiments, the compositional analysis results shown below represent the composition of Ag, Au, Te, and S in the entire nanoparticle in atomic percent. The AgAuTeS compound of the present invention (Ag x Au y (Te 1-a S a ) zRegarding the atomic proportions of each constituent element, x and y can be converted by dividing the concentrations (atomic %) of Ag and Au in the table below by 100. Also, z can be converted by dividing the sum of the Te concentration (atomic %) and the S concentration (atomic %) by 100. Table 1 below shows the atomic proportion a of S in the chalcogen element calculated based on the analysis results and the x, y, and z calculated above, as well as the values ​​of x / (x+y) and (x+y) / z.

[0049] [Table 1]

[0050] Referring to Table 1, the overall trend in composition of the AgAuTeS compound nanoparticles synthesized in this embodiment by varying the reaction temperature is that the atomic proportion of Au in the metal components (Ag, Au) is low. Furthermore, it can be seen that the atomic proportion of Te is high in the chalcogen element. However, when examined more precisely in relation to the reaction temperature, at reaction temperatures of 120°C or higher, there is a tendency for the atomic proportion of Au to increase and the atomic proportion of S to decrease with increasing temperature.

[0051] Next, the crystal structure of the AgAuTeS compound nanoparticles synthesized in this embodiment was confirmed by XRD analysis. The XRD analyzer used was a Rigaku Smart-Lab-3K, with the characteristic X-ray set to CuKα and the analysis condition set to 1° / min. Figure 3 shows the XRD diffraction patterns of the AgAuTeS compound nanoparticles synthesized at each reaction temperature.

[0052] Referring to Figure 3, it is estimated that when the reaction temperature is relatively low (below 120°C), the AgAuTeS compound nanoparticles have a crystal structure similar to that of an AgTe compound (Ag2Te or Ag5Te3 or a mixture thereof). On the other hand, when the reaction temperature is relatively high (above 135°C), the AgAuTeS compound nanoparticles are estimated to have a crystal structure similar to that of an AgAuTe compound (Ag3AuTe2). This estimation is consistent with the results of the compositional analysis of the AgAuTeS compound nanoparticles described above, in which the proportion of Au atoms was small at low temperatures and increased with increasing temperature.

[0053] [Absorption spectroscopy and emission spectroscopy] To evaluate the photoresponsiveness of the AgAuTeS compound nanoparticles synthesized in this embodiment, absorption and emission spectra were measured. The absorption spectrum was measured using a UV-Vis spectrophotometer (JASCO Corporation V770iRM) with the nanoparticle solution placed in a quartz cell with a path length of 1 cm. The wavelength range measured was 400 nm to 2400 nm. The emission spectrum was measured after adjusting the sample so that the absorbance at 680 nm was 0.1. For the measurement, light irradiation (680 nm) was performed from a laser light source (Solabo Japan RILS50-01). A multi-channel spectrometer (Hamamatsu Photonics K.K. PMA-12, C10028-01) was used as the detector. The measurement conditions were an excitation wavelength of 680 nm and a measurement range of 900 to 1685 nm.

[0054] Figure 4 shows the absorption spectrum (Figure 4(a)) and emission spectrum (Figure 4(b)) measurements of the AgAuTeS compound nanoparticles synthesized in this embodiment. Table 2 shows the peak wavelength of the exciton peak and the long-wavelength absorption edge wavelength obtained from the absorption spectrum measurements for each AgAuTeS compound nanoparticle. Table 2 also shows the emission quantum efficiency (QY) obtained from the emission spectrum measurements and the emission spectrum measurements of the standard sample, indocyanine green in an ethanol solution.

[0055] [Table 2]

[0056] From the absorption spectrum measurements in Figure 4(a), the absorption spectra of AgAuTeS compound nanoparticles synthesized at reaction temperatures of 80°C and 100°C were almost identical, with an absorption edge wavelength of approximately 1800 nm. Similarly, the absorption spectra of AgAuTeS compound nanoparticles synthesized at reaction temperatures above 120°C were also almost identical, with an absorption edge wavelength of approximately 2000 nm. Therefore, light absorption in the near-infrared region was observed for all AgAuTeS compound nanoparticles. However, the absorption spectra of AgAuTeS compound nanoparticles synthesized at 80°C and 100°C showed absorption peaks around 1250 nm and 1320 nm, which are presumed to be exciton peaks. Exciton peaks appear in semiconductor nanoparticles with fine particle size, good uniformity, and crystalline properties. The absorption spectrum results for AgAuTeS compound nanoparticles synthesized at 80°C and 100°C are consistent with the particle size and particle size distribution (standard deviation) measurements described above.

[0057] Referring to the emission spectrum measurement results in Figure 4(b), emission was observed in two AgAuTeS compound nanoparticles synthesized at reaction temperatures of 80°C and 100°C. Of these, the one synthesized at 80°C had a higher emission quantum efficiency. In contrast, no emission was observed in AgAuTeS compound nanoparticles synthesized at a reaction temperature of 120°C or higher.

[0058] The results of the particle size and particle size distribution measurements, compositional analysis, XRD analysis, and absorption / emission spectrum measurements described above suggest a suitable configuration for semiconductor nanoparticles made of AgAuTeS compounds and the resulting suitable optical properties. Specifically, the composition of AgAuTeS compound nanoparticles, particularly the proportion of Au atoms (y) and S atoms (a), changes depending on the reaction temperature during synthesis. This is presumed to be due to differences in the framework (crystal structure) formed at high and low reaction temperatures. In other words, it is presumed that the crystal structure formed at high temperatures easily incorporates Au, resulting in AgAuTeS compound nanoparticles with a high proportion of Au atoms. Furthermore, AgAuTeS compound nanoparticles synthesized at relatively low temperatures exhibit good uniformity in particle size distribution. In addition, it was found that the AgAuTeS compound nanoparticles obtained in this embodiment have an absorption edge wavelength in the near-infrared region and can also exhibit emission.

[0059] Second Embodiment In this embodiment, the reaction temperature was set to 80°C, which was estimated to be optimal from the first embodiment, and AgAuTeS compound nanoparticles were synthesized by varying the reaction time. Then, the AgAuTeS compound nanoparticles were measured and evaluated using the same criteria as in the first embodiment.

[0060] The method for synthesizing AgAuTeS compound nanoparticles in this embodiment is basically the same as the synthesis method in the first embodiment. In this embodiment, the reaction temperature was set to 80°C after adding the S precursor (DDT) and solvent (OLA) to a test tube containing weighed Ag precursors and Au precursors, and the reaction time was set to 15 minutes, 30 minutes, 60 minutes, and 120 minutes, and AgAuTeS compound nanoparticles were synthesized at each reaction time.

[0061] Then, TEM observation, particle size distribution and average particle size measurements were performed on the AgAuTeS compound nanoparticles synthesized at each reaction time, and compositional analysis (EDX) was carried out. Furthermore, absorption and emission spectra measurements were performed on the AgAuTeS compound nanoparticles synthesized in this embodiment. These measurements and analyses were performed using the same methods and conditions as in the first embodiment.

[0062] As a result of the investigation in this embodiment, Figure 5 shows TEM images of AgAuTeS compound nanoparticles synthesized with reaction times of 15 minutes, 30 minutes, 60 minutes, and 120 minutes (reaction temperature 80°C). Table 3 shows the results of the measurement of the average particle size and standard deviation of the AgAuTeS compound nanoparticles, as well as the results of the compositional analysis by EDX.

[0063] [Table 3]

[0064] From the TEM image in Figure 5, it can be seen that most of the AgAuTeS compound nanoparticles synthesized in this embodiment are spherical. Only the AgAuTeS compound nanoparticles synthesized after a reaction time of 120 minutes are polygonal in shape. Considering the particle shape in the TEM image, and referring to Table 3 to examine the particle size and particle size distribution (standard deviation), it is estimated that the optimal reaction time for synthesizing particularly suitable semiconductor nanoparticles is 60 minutes. The AgAuTeS compound nanoparticles synthesized after a reaction time of 120 minutes were coarse and highly variable.

[0065] Figure 6 shows the measurement results of the absorption spectrum (Figure 6(a)) and emission spectrum (Figure 6(b)) of the AgAuTeS compound nanoparticles synthesized in this embodiment. Table 4 also shows the peak wavelength of the exciton peak and the long-wavelength absorption edge wavelength obtained from the absorption spectrum measurement results for each AgAuTeS compound nanoparticle.

[0066] [Table 4]

[0067] Referring to Figure 6(a) and Table 4, the absorption spectra of AgAuTeS compound nanoparticles reacted for 15 to 60 minutes show an absorption edge wavelength in the near-infrared region (1800 nm), with an absorption peak (exciton peak) observed around 1250 nm to 1450 nm. Furthermore, referring to Figure 6(b), luminescence was also observed in AgAuTeS compound nanoparticles reacted for 15 to 60 minutes. As described above, AgAuTeS compound nanoparticles reacted for less than 60 minutes exhibited good shape and particle size distribution, and this result is consistent with the measurement results of the absorption and emission spectra.

[0068] From the results of this embodiment, it is estimated that the optimal reaction time when the reaction temperature is 80°C is 60 minutes. However, it can be said that suitable semiconductor nanoparticles can be synthesized over a relatively wide range of reaction times.

[0069] Third Embodiment From the results of the second embodiment, it was confirmed that a reaction time of 60 minutes is optimal for achieving uniformity of particle shape and particle size. On the other hand, in the first embodiment, the reaction time was 15 minutes. Therefore, in this embodiment, the reaction time was set to 60 minutes, which is estimated to be optimal, and AgAuTeS compound nanoparticles were synthesized by changing the reaction temperature. Then, the AgAuTeS compound nanoparticles were measured and evaluated using the same criteria as in the first embodiment.

[0070] In this embodiment as well, AgAuTeS compound nanoparticles were synthesized using basically the same procedure as in the first embodiment. In this embodiment, AgAuTeS compound nanoparticles were synthesized by adding the S precursor (DDT) and solvent (OLA) to a test tube containing weighed Ag precursors and Au precursors, and then allowing a reaction time of 60 minutes while varying the reaction temperatures to 60°C, 80°C, 100°C, and 120°C.

[0071] Then, TEM observation, particle size distribution and average particle size measurements were performed on the AgAuTeS compound nanoparticles synthesized at each reaction time, and compositional analysis (EDX) was carried out. Furthermore, absorption and emission spectra measurements were performed on the AgAuTeS compound nanoparticles synthesized in this embodiment. These measurements and analyses were performed using the same methods and conditions as in the first embodiment.

[0072] As a result of the investigation in this embodiment, Figure 7 shows TEM images of AgAuTeS compound nanoparticles synthesized at reaction temperatures of 60°C, 80°C, 100°C, and 120°C (reaction time 60°C). Table 5 shows the results of the measurement of the average particle size and standard deviation of the AgAuTeS compound nanoparticles, as well as the results of the compositional analysis by EDX.

[0073] [Table 5]

[0074] Referring to the TEM image in Figure 7, the results appear to be similar to those of the first embodiment. In this embodiment as well, particle aggregation occurs at the higher reaction temperature (120°C). In the first embodiment, nearly spherical particles with little aggregation were synthesized even at 120°C, but in this embodiment, it is thought that the increased reaction time had an effect.

[0075] Figure 8 shows the measurement results of the absorption spectrum (Figure 8(a)) and emission spectrum (Figure 8(b)) of the AgAuTeS compound nanoparticles synthesized in this embodiment. Table 6 also shows the peak wavelength of the exciton peak and the long-wavelength absorption edge wavelength obtained from the absorption spectrum measurement results for each AgAuTeS compound nanoparticle.

[0076] [Table 6]

[0077] In this embodiment, AgAuTeS compound nanoparticles with good shape and particle size distribution (standard deviation) also showed good results in absorption and emission spectra. AgAuTeS compound nanoparticles reacted at 80°C and 60°C showed an absorption edge wavelength in the near-infrared region (1700 nm) in the absorption spectrum, and absorption peaks (exciton peaks) were observed at 1350 nm and 1450 nm. Furthermore, emission was also confirmed for AgAuTeS compound nanoparticles reacted at 80°C and 60°C.

[0078] Fourth Embodiment In the embodiments described so far, silver acetate (Ag(OAc)) was used as the Ag precursor and chloro(dimethyl sulfide) gold ((CH3)2SAuCl) was used as the Au precursor. In this embodiment, AgAuTeS compound nanoparticles were synthesized by changing the Ag precursor or Au precursor. Then, the AgAuTeS compound nanoparticles were measured and evaluated using the same criteria as in the first embodiment.

[0079] In the method for synthesizing AgAuTeS compound nanoparticles of the first embodiment, AgAuTeS compound nanoparticles were synthesized using the same Au complex and S precursor as in the first embodiment, except that 0.3 mmol of silver chloride (AgCl) was used as the Ag precursor. Furthermore, in the synthesis method of the first embodiment, AgAuTeS compound nanoparticles were synthesized using the same Ag complex and S precursor as in the first embodiment, except that 0.1 mmol of chlorauric acid (HAuCl4) was used as the Au precursor. In both synthesis methods, the reaction temperature was 80°C and the reaction time was 60 minutes.

[0080] Two types of synthesized AgAuTeS compound nanoparticles were subjected to TEM observation, particle size distribution and average particle size measurement, and compositional analysis (EDX). Furthermore, absorption and emission spectra were measured for the AgAuTeS compound nanoparticles synthesized in this embodiment. These measurements and analyses were performed using the same methods and conditions as in the first embodiment.

[0081] Figure 9 shows TEM images of two types of AgAuTeS compound nanoparticles synthesized using AgCl as the Ag precursor and HAuCl4 as the Au precursor. Table 7 shows the results of the measurement of the average particle size and standard deviation of these AgAuTeS compound nanoparticles, as well as the results of the compositional analysis by EDX. For comparison, Figure 9 and Table 7 also show the results of AgAuTeS compound nanoparticles synthesized using Ag(OAc) as the Ag precursor and (CH3)2SAuCl) as the Au precursor under the same reaction conditions (80°C, 60 minutes). Specifically, the results for AgAuTeS compound nanoparticle No. 8 of the third embodiment are shown.

[0082] [Table 7]

[0083] Referring to the TEM image in Figure 9, it can be said that there is no significant difference in particle shape or particle size even if the Ag precursor or Au precursor is different from that of the first embodiment. However, referring to the compositional analysis results in Table 7, the Ag precursor or Au precursor used in this embodiment has a relatively low proportion of Au atoms. Furthermore, XRD analysis was performed on the AgAuTeS compound nanoparticles synthesized in this embodiment, and the diffraction pattern was similar to the diffraction pattern at a reaction temperature of 80°C in the first embodiment, suggesting that it has a crystal structure similar to that of the AgTe compound (Ag2Te).

[0084] Figure 10 shows the absorption spectrum (Figure 10(a)) and emission spectrum (Figure 10(b)) of AgAuTeS compounds synthesized using AgCl as the Ag precursor. Figure 11 shows the absorption spectrum (Figure 11(a)) and emission spectrum (Figure 11(b)) of AgAuTeS compounds synthesized using HAuCl4 as the Au precursor. Table 8 shows the peak wavelength of the exciton peak and the long-wavelength absorption edge wavelength obtained from the absorption spectrum measurements for each AgAuTeS compound nanoparticle.

[0085] [Table 8]

[0086] The AgAuTeS compound nanoparticles synthesized in this embodiment all exhibited absorption edges in the near-infrared region (around 1750-1800 nm) in their absorption spectra, and also showed exciton peaks. Furthermore, emission was confirmed from these AgAuTeS compound nanoparticles by emission spectroscopy. However, the emission quantum efficiency was higher for the AgAuTeS compound nanoparticles synthesized in the third embodiment than for the AgAuTeS compound nanoparticles of this embodiment. Nevertheless, since suitable AgAuTeS compound nanoparticles were synthesized in this embodiment as well, it can be said that the Ag precursor and Au precursor are not limited to specific compounds (complexes).

[0087] Fifth Embodiment In this embodiment, AgAuTeS compound nanoparticles were synthesized by changing the composition ratio of the metal components during nanoparticle synthesis. Specifically, the ratio of the amount of Ag added to the total amount of metal components added (Ag addition ratio: amount of Ag added / (amount of Ag added + amount of Au added)) was changed.

[0088] In this embodiment, in the method for synthesizing AgAuTeS compound nanoparticles of the first embodiment, when weighing and collecting Ag precursor (Ag(OAc)) and Au precursor ((CH3)2SAuCl) in a test tube, the amount of each precursor collected was adjusted to change the Ag charging ratio. At this time, two types of AgAuTeS compound nanoparticles were synthesized with Ag charging ratios of 0.25 (0.1 mmol Ag precursor + 0.3 mmol Au precursor) and 0.5 (0.2 mmol Ag precursor + 0.2 mmol Au precursor). Other raw materials and synthesis operations were the same as in the first embodiment. In addition, the reaction temperature was 80°C and the reaction time was 60 minutes in both synthesis.

[0089] Two types of synthesized AgAuTeS compound nanoparticles were subjected to TEM observation, particle size distribution and average particle size measurement, and compositional analysis (EDX). Furthermore, absorption and emission spectra were measured for the AgAuTeS compound nanoparticles synthesized in this embodiment. These measurements and analyses were performed using the same methods and conditions as in the first embodiment.

[0090] Figure 12 shows TEM images of the two types of AgAuTeS compound nanoparticles synthesized in this embodiment. Table 9 shows the results of the measurement of the average particle size and standard deviation of these AgAuTeS compound nanoparticles, as well as the results of the compositional analysis by EDX. For comparison, Figure 12 and Table 9 also show the results of AgAuTeS compound nanoparticles synthesized under the same reaction conditions (80°C, 60 minutes) with the same Ag charge ratio (0.75) as in the first embodiment. That is, the results show that these are AgAuTeS compound nanoparticles No. 8 of the third embodiment.

[0091] [Table 9]

[0092] As seen in the TEM image in Figure 12, the AgAuTeS compound nanoparticles synthesized with an Ag loading ratio of 0.25 aggregated, making it impossible to distinguish individual particles. On the other hand, when the Ag loading ratio was set to 0.25 and 0.75, AuTeS compound nanoparticles with suitable shape and particle size distribution were synthesized. This was also confirmed by the compositional analysis results in Table 9, which showed that the AgAuTeS compound nanoparticles synthesized with an Ag loading ratio of 0.25 had a small proportion of Ag atoms while having an excessive proportion of Au atoms.

[0093] Figure 13 shows the measurement results of the absorption spectrum (Figure 13(a)) and emission spectrum (Figure 13(b)) of the AgAuTeS compound nanoparticles synthesized in this embodiment. Table 10 also shows the peak wavelength of the exciton peak and the long-wavelength absorption edge wavelength obtained from the absorption spectrum measurement results for each AgAuTeS compound nanoparticle.

[0094] [Table 10]

[0095] AgAuTeS compound nanoparticles, whose shape and particle size distribution were confirmed to be good by TEM observation, also showed good results in absorption and emission spectra. AgAuTeS compound nanoparticles with Ag content ratios of 0.5 and 0.75 showed an absorption edge wavelength in the near-infrared region (1800 nm) in the absorption spectrum, and an exciton peak was observed around 1450 nm to 1500 nm. Emission was also confirmed from these AgAuTeS compound nanoparticles. AgAuTeS compound nanoparticles with an Ag content ratio of 0.25 had an absorption edge in the near-infrared region, but no emission was observed. [Industrial applicability]

[0096] As explained above, the AgAuTeS compound (Ag) according to the present invention x Au y (Te 1-a S a ) z Semiconductor nanoparticles, primarily composed of ), exhibit suitable photoresponsiveness in long-wavelength regions such as the near-infrared region through the combination of chalcogen elements and the setting of an appropriate composition.

[0097] The semiconductor nanoparticles according to the present invention are expected to have applications in light-emitting elements and fluorescent materials used in display devices and marker materials for detecting bio-related substances, as well as in photoelectric conversion elements and photodetectors mounted in solar cells and light sensors. In particular, the present invention is useful for photodetectors and light-emitting elements applied to LIDAR and SWIR image sensors used in the long-wavelength regions of the near-infrared (NIR) and short-wave infrared (SWIR) regions.

Claims

1. Semiconductor nanoparticles containing an AgAuTeS compound represented by the following formula, consisting of Ag, Au, Te, and S. 【Chemistry 1】 (In the formula, x is the atomic percentage of Ag, where 0.50 ≤ x ≤ 0.65; y is the atomic percentage of Au, where 0.01 ≤ y ≤ 0.1; z is the sum of the atomic percentages of the chalcogen elements Te and S, where 0.25 ≤ z ≤ 0.50; and a is the atomic percentage of S in the chalcogen elements, where 0 < a < 1.)

2. The semiconductor nanoparticle according to claim 1, wherein the AgAuTeS compound is 0.1 ≤ a ≤ 0.

5.

3. The semiconductor nanoparticle according to claim 1 or claim 2, wherein the AgAuTeS compound is 0.9 ≤ x / (x + y) < 1.

0.

4. Semiconductor nanoparticles according to claim 1 or claim 2, wherein the average particle size is 1 nm or more and 20 nm or less.

5. The semiconductor nanoparticle according to claim 1 or claim 2, wherein the absorption edge wavelength on the long-wavelength side of the absorption spectrum is 1200 nm or more.

6. The semiconductor nanoparticle according to claim 1 or claim 2, wherein the peak wavelength of the emission spectrum is 1000 nm or more.

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