Semiconductor nanoparticles composed of agau s compounds

Abstract

The present application is a semiconductor nanoparticle composed of a semiconductor crystal containing a compound of Ag, Au, and S as essential constituent elements. In the AgAuS compound constituting the semiconductor nanoparticle, the total content of Ag, Au, and S is 95% by mass or more. In addition, the compound is preferably an AgAuS ternary compound represented by the general formula Ag (nx) Au (ny) S (nz) . In the general formula, n is an arbitrary positive integer. x, y, z represent the proportion of the number of atoms of each atom of Ag, Au, and S in the compound, and are real numbers satisfying 0 < x, y, z ≤ 1. In addition, x / y is 1 / 7 or more and 7 or less.

Description

Technical Field

[0001] This invention relates to semiconductor nanoparticles composed of AgAuS-based compounds. Specifically, it relates to semiconductor nanoparticles with a novel structure derived from ternary compounds composed of Ag, Au, and S. Background Technology

[0002] Semiconductors exhibit quantum confinement by being composed of tiny nanoparticles, displaying a band gap corresponding to their particle size. Therefore, by controlling the composition and particle size of semiconductor nanoparticles, the band gap can be tuned, allowing for the arbitrary setting of emission or absorption wavelengths. Semiconductor nanoparticles utilizing this property are also known as quantum dots (QDs), and their applications in various technological fields are highly anticipated.

[0003] For example, research is underway on the application of semiconductor nanoparticles in light-emitting elements and fluorescent substances used in display devices or bioassay markers. As mentioned above, in addition to the ability to freely control the emission wavelength through particle size control, semiconductor nanoparticles also exhibit sufficiently narrow emission peak widths compared to organic pigments and are more stable under excitation light. Therefore, applications in light-emitting elements and the like are expected.

[0004] In addition, semiconductor nanoparticles are also expected to be used in photoelectric conversion elements or light receiving elements mounted on solar cells or photosensors. Besides the ability to control the absorption wavelength through particle size, they also possess the following characteristics: high quantum efficiency and high absorption coefficient. These properties contribute to the miniaturization and thinning of semiconductor devices.

[0005] Furthermore, as specific components of semiconductor nanoparticles, semiconductor nanoparticles composed of the following are known: Group 12-16 compound semiconductors such as CdS, CdSe, and CdTe; binary compound semiconductors such as Group 14-16 compound semiconductors such as PbS and PbSe; and ternary compound semiconductors such as Group 11-13-16 compound semiconductors such as AgInTe2 (Patent Documents 1-3).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-243507

[0009] Patent Document 2: Japanese Patent Application Publication No. 2004-352594

[0010] Patent Document 3: Japanese Patent Application Publication No. 2017-014476 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] Semiconductor nanoparticles currently being applied to the various purposes described above are still in the research stage, and optimal semiconductor nanoparticles, including their manufacturing methods, have not yet been found. In this context, there is an increasing demand for the development of novel compound semiconductor nanoparticles that utilize the aforementioned special properties arising from quantum confinement effects and possess practical characteristics such as biocompatibility (low toxicity composition). This invention was made against this background, providing a semiconductor nanoparticle composed of a novel compound semiconductor not previously reported in terms of composition, exhibiting suitable light emission / absorption properties and biocompatibility.

[0013] Methods for solving problems

[0014] The present invention, which solves the above-mentioned problems, is a semiconductor nanoparticle composed of a semiconductor crystal containing a compound with Ag, Au, and S as essential constituent elements, wherein the total content of Ag, Au, and S in the compound is 95% by mass or more.

[0015] In existing research, Ag and Au are each used as constituent elements of semiconductor nanoparticles, but there are no specific research examples regarding the properties of ternary compound semiconductor nanoparticles containing both Ag and Au. In this regard, according to the inventors' research, it has been confirmed that AgAuS-based compound semiconductors exhibit suitable light emission / absorption properties through nanoparticle formation and adjustment of the Ag and Au composition.

[0016] Furthermore, both Ag and Au are chemically stable metals, known since ancient times for their biocompatibility. Moreover, sulfur (S) is an essential element for living organisms, meaning it also possesses biocompatibility. Therefore, AgAuS-based compound semiconductors can be expected to be used in applications such as labeling or DNA chips, and other fluorescent materials for the human body.

[0017] The semiconductor nanoparticles composed of AgAuS-based compound semiconductors and their manufacturing methods, which are involved in this invention, will be described below.

[0018] The present invention relates to the composition of semiconductor nanoparticles.

[0019] As described above, the semiconductor nanoparticles involved in this invention are semiconductor nanoparticles composed of compounds with Ag, Au, and S as essential constituent elements. Specifically, the compounds composed of Ag, Au, and S are semiconductor nanoparticles with the general formula Ag (nx) Au (ny) S (nz)This represents a ternary AgAuS compound. Here, n is any positive integer. x, y, and z represent the atomic ratios of Ag, Au, and S atoms in the compound, and are real numbers where 0 < x, y, z ≤ 1. Furthermore, for the atomic ratios x and y of Ag and Au, x / y is greater than or equal to 1 / 7 and less than or equal to 7. As mentioned above, the atomic ratio z of S is a real number where 0 < z ≤ 1, but preferably a real number where z ≥ (x + y) / 2.

[0020] More specifically, the AgAuS-based compounds in this invention can include Ag1Au7S4, AgAu3S2, Ag3Au5S4, AgAuS, Ag5Au3S4, Ag3AuS2, and Ag7AuS4. These specific AgAuS-based compounds are compounds with stoichiometric compositions where nx, ny, and nz are integers; however, the compounds constituting the semiconductor nanoparticles of this invention are not limited to compounds with such stoichiometric compositions.

[0021] Furthermore, regarding the atomic ratio x and y of Ag and Au, it is more preferable that x / y is 0.3 or more and 3.6 or less. Even more preferable is that x / (x+y) is a real number of 0.33 or more and 0.78 or less. AgAuS, Ag5Au3S4, and Ag3AuS2, as AgAuS-based compounds with the stoichiometric compositions listed above, meet these conditions. Semiconductor nanoparticles composed of these compounds exhibit high luminescence quantum yields, demonstrating effective characteristics as luminescent elements, etc.

[0022] As described above, the semiconductor nanoparticles involved in this invention are made of Ag (nx) Au (ny) S (nz) The indicated composition is an AgAuS-based compound. This AgAuS-based compound is not limited to a single phase but can also consist of a mixed phase. For example, it can be an AgAuS-based compound with the above stoichiometric composition (Ag3AuS2, etc.) and an AgAuS-based compound with a non-stoichiometric composition (Ag... (nx) Au (ny) S (nz) The mixture of nx, ny, and nz (where nx, ny, and nz are real numbers that are not integers within the range mentioned above).

[0023] The semiconductor nanoparticles of the present invention are composed of semiconductor crystals of compounds with Ag, Au, and S as essential constituent elements, as described above. The total content of Ag, Au, and S in the semiconductor crystal is 95% by mass or more. Elements other than the essential constituent elements Ag, Au, and S that may be present include Ge, Si, Sn, Pb, O, Se, and Te, etc., and these elements are acceptable if they are less than 5% by mass. Preferably, the total content of Ag, Au, and S in the compound is 99% by mass or more, more preferably 99.9% by mass or more. It should be noted that the composition values ​​of the compound here refer to the semiconductor crystal itself within the semiconductor nanoparticles and do not contain the protective agent components described later.

[0024] The average particle size of the semiconductor nanoparticles involved in this invention is preferably 2 nm to 20 nm. 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 achieve suitable light emission / light absorption characteristics by adjusting the band gap, the above-mentioned average particle size is preferred. It should be noted that the average particle size of the semiconductor nanoparticles can be obtained by observing multiple (preferably more than 100) particles using an electron microscope such as TEM, measuring the particle size of each particle, and calculating the average number of particles.

[0025] Furthermore, the semiconductor nanoparticles of the present invention preferably have any of the following as a protective agent bonded to their surface: alkylamines with 4 to 20 carbon atoms in the alkyl chain, alkenylamines with 4 to 20 carbon atoms in the alkenyl chain, alkylcarboxylic acids with 3 to 20 carbon atoms in the alkyl chain, alkenylcarboxylic acids with 3 to 20 carbon atoms in the alkenyl chain, alkanethiols with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphines with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphine oxides with 4 to 20 carbon atoms in the alkyl chain, triphenylphosphine, and triphenylphosphine oxide. In processing semiconductor nanoparticles, solutions (sometimes called slurries or inks) prepared by dispersing semiconductor nanoparticles in a suitable dispersion medium are often used. The aforementioned protective agents can be used to suppress the aggregation of semiconductor nanoparticles in the solution to form a homogeneous solution, etc. Additionally, the protective agent also plays a role in forming nanoparticles with a suitable average particle size by being added to the reaction system together with the raw materials during the synthesis process of the AgAuS compound. It should be noted that the protective agent can be applied individually or in combination with one or more of the above-mentioned alkylamines, alkenylamines, alkylcarboxylic acids, alkenylcarboxylic acids, alkylthiols, trialkylphosphines, trialkylphosphine oxides, triphenylphosphines, and triphenylphosphine oxides.

[0026] In summary, semiconductor nanoparticles, by adjusting their band gap through quantum confinement effects according to their particle size, thereby altering their light absorption characteristics. In the semiconductor nanoparticles of this invention, the absorption wavelength at the long-wavelength side of the absorption spectrum is preferably 600 nm or higher. Therefore, the semiconductor nanoparticles possess absorption / responsiveness to light from the visible light region to the near-infrared region.

[0027] By coating / loading the semiconductor nanoparticles involved in this invention onto a suitable substrate / carrier, they can be applied to the various applications described above, such as light-emitting elements. There are no particular limitations on the composition, shape, or size of the substrate or carrier. Examples of plate-like or foil / film-like substrates include glass, quartz, silicon, ceramics, or metals. Examples of granular / powder-like carriers include inorganic oxides such as ZnO, TiO2, WO3, SnO2, In2O3, and Al2O3. Alternatively, semiconductor nanoparticles can be loaded onto the aforementioned inorganic oxide carriers and further fixed onto the substrate.

[0028] Furthermore, when coating / loading semiconductor nanoparticles onto a substrate / carrier, as mentioned above, solutions / slurries / inks prepared by dispersing semiconductor nanoparticles in a suitable dispersion medium are often used. Chloroform, toluene, cyclohexane, hexane, etc., can be used as dispersion media. Moreover, coating methods for semiconductor nanoparticle solutions, etc., can include dip coating and spin coating, and loading methods can include various methods such as drop casting, impregnation, and adsorption.

[0029] B. The present invention relates to a method for manufacturing semiconductor nanoparticles.

[0030] Semiconductor nanoparticles utilizing the AgAuS-based compound semiconductor of this invention can be manufactured by mixing an Ag precursor, an Au precursor, and an S precursor (if desired) as a sulfur source in a reaction solvent, and then heating the reaction system composed of these components at a temperature of 100°C to 200°C. It should be noted that, as described above, at least one of the following is preferably added as a protective agent to the reaction system: alkylamines with 4 to 20 carbon atoms in the alkyl chain, alkenylamines with 4 to 20 carbon atoms in the alkenyl chain, alkylcarboxylic acids with 3 to 20 carbon atoms in the alkyl chain, alkenylcarboxylic acids with 3 to 20 carbon atoms in the alkenyl chain, alkylthiols with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphines with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphine oxides with 4 to 20 carbon atoms in the alkyl chain, triphenylphosphine, and triphenylphosphine oxide.

[0031] For the Ag and Au precursors used as raw materials, Ag salts or Ag complexes, and Au salts or Au complexes are applied, respectively. The Ag and Au precursors preferably contain salts or complexes of monovalent Ag and monovalent Au, respectively. However, for the Au precursor, a precursor containing trivalent Au can be used. This is because, during the synthesis of semiconductor nanoparticles, trivalent Au is reduced to monovalent Au by a solvent or coexisting sulfur compounds. Furthermore, at least one of the Ag and Au precursors preferably uses a complex having a ligand containing a sulfur (S) atom. In this case, the sulfur atom contained in the ligand of the Ag and / or Au complex can be used as a sulfur supply source for synthesizing the compound.

[0032] Suitable Ag precursors include silver acetate (Ag(OAc)), silver nitrate, silver carbonate, silver oxide, silver oxalate, silver chloride, silver iodide, and silver (I) cyanide salts. Additionally, suitable Au precursors include Au resin salts (C... 10 H 18 Au2S2 (CAS 68990-27-2), gold chloride (dimethyl sulfide) (I)((CH3)2SAuCl), gold iodide (I), gold sulfite (I) salt, chloroauric acid (III), gold acetate (III), gold cyanide (I) salt, gold cyanide (III) salt, 1,10-phenanthroline gold (III), etc. In addition, sulfur compounds serving as S precursors, besides elemental sulfur, can include compounds such as thiourea, alkylthiourea, thioacetamide, and alkathiols; β-dithioketones, dithiols, xanthates, and diethyldithiocarbamates. It should be noted that Ag complexes and Au complexes can be complexes with ligands containing S atoms, or compounds with added S atoms.

[0033] Here, the composition of the synthesized AgAuS-based compounds (general formula Ag) is as follows: (nx) Au (ny) S (nz) The values ​​of x and y in the equation can be adjusted by the mixing ratio (atomic ratio) of the Ag and Au precursors. To obtain a suitable AgAuS-based compound, when the ratio of the metal atoms contained in the Ag and Au precursors (Ag:Au) is set to a:b, it is preferable that a:b is set between 0.78:0.22 and 0.14:0.86 in terms of atomic ratio. Furthermore, regarding the amount of S (c) in the reaction system, it is preferably set to 0.25 to 4 or less in terms of atomic ratio relative to the total number of Ag and Au atoms in the reaction system. However, even if residual S is present in the reaction system, its effect on the composition of the AgAuS-based compound is small.

[0034] The reaction system in the synthesis of semiconductor nanoparticles can be generated without solvents or with solvents. When using solvents, octadecene, tetradecane, oleic acid, oleylamine, dodecyl mercaptan, or mixtures thereof can be used.

[0035] The heating temperature (reaction temperature) of the reaction system consisting of Ag precursor, Au precursor, S precursor, and protecting agent is set to 50°C to 200°C. Below 50°C, it is difficult to synthesize AgAuS-based compounds. On the other hand, above 200°C, there is a problem that Au may form nanoparticles independently without forming the desired compound composition. The average particle size of the semiconductor nanoparticles increases with increasing reaction temperature, but within the above temperature range, it rarely exceeds a suitable average particle size. A more suitable reaction temperature is 100°C to 165°C. Furthermore, the heating time (reaction time) can be adjusted according to the amount of raw materials input, preferably set to 1 minute to 60 minutes. It should be noted that a stirred reaction system is preferred in the synthesis reaction of semiconductor nanoparticles.

[0036] After the synthesis reaction of semiconductor nanoparticles is completed, the reaction system is cooled as needed, and the semiconductor nanoparticles are recovered. At this time, an alcohol (ethanol, methanol, etc.) is added as a non-solvent to precipitate the nanoparticles, or the semiconductor nanoparticles can be precipitated and recovered by centrifugation, etc. The particles are then temporarily washed with alcohol (ethanol, methanol, etc.) and then uniformly dispersed in a good solvent such as chloroform.

[0037] The effects of the invention

[0038] As described above, the present invention comprises semiconductor nanoparticles composed of AgAuS-based compounds. AgAuS-based compounds are a novel composition for semiconductor nanoparticles, exhibiting suitable optical properties as nanoparticles. Furthermore, since their constituent elements are low-toxicity elements with biocompatibility, they are expected to be used not only in conventional semiconductor devices such as light-emitting elements, but also in biomarkers and other applications. Attached Figure Description

[0039] [ Figure 1 [ ] is a diagram illustrating the manufacturing process of AgAuS semiconductor nanoparticles according to the first and second embodiments.

[0040] [ Figure 2 [Image 1] is a TEM image of the AgAuS semiconductor nanoparticles manufactured in the first embodiment.

[0041] [ Figure 3 [1] is a graph showing the relationship between the atomic ratio a:b of the AgAuS semiconductor nanoparticles manufactured in the first embodiment and the average particle size.

[0042] [ Figure 4 [Image] is a diagram showing the XRD diffraction pattern of the AgAuS semiconductor nanoparticles manufactured in the first embodiment.

[0043] [ Figure 5a [Image] is a diagram showing the XRD diffraction pattern of the AgAuS semiconductor nanoparticles (atomic ratio a:b = 1:0) manufactured in the first embodiment.

[0044] [ Figure 5b [Image] is a diagram showing the XRD diffraction pattern of the AgAuS semiconductor nanoparticles (atomic ratio a:b = 0.60:0.40) manufactured in the first embodiment.

[0045] [ Figure 5c [Image] is a diagram showing the XRD diffraction pattern of the AgAuS semiconductor nanoparticles (atomic ratio a:b = 0:1) manufactured in the first embodiment.

[0046] [ Figure 6 [1] is a graph showing the measurement results of the absorption spectrum of the AgAuS semiconductor nanoparticles manufactured in the first embodiment.

[0047] [ Figure 7 [Figure 1] shows the emission spectrum measurement results of the AgAuS semiconductor nanoparticles manufactured in the first embodiment.

[0048] [ Figure 8 [1] is a graph showing the measurement results of the emission spectrum of the AgAuS semiconductor nanoparticles (long wavelength region) manufactured in the first embodiment.

[0049] [ Figure 9 [1] is a graph showing the relationship between the atomic ratio a:b of the AgAuS semiconductor nanoparticles manufactured in the first embodiment and the wavelength at the absorption end.

[0050] [ Figure 10 [1] is a graph showing the relationship between the input atomic ratio a:b of the AgAuS semiconductor nanoparticles manufactured in the first embodiment and the luminescence quantum yield.

[0051] [ Figure 11 [Image 1] is a TEM image of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0052] [ Figure 12 [1] is a graph showing the relationship between the reaction temperature and the average particle size of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0053] [ Figure 13[1] is a graph showing the measurement results of the absorption spectrum of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0054] [ Figure 14 [1] is a graph showing the relationship between the reaction temperature and the absorption wavelength of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0055] [ Figure 15 [Figure 1] is a graph showing the measurement results of the emission spectrum of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0056] [ Figure 16 [1] is a graph showing the relationship between the reaction temperature and the luminescence quantum yield of the AgAuS semiconductor nanoparticles manufactured in the second embodiment.

[0057] [ Figure 17 [Image] is a diagram showing the XRD diffraction patterns of the AgAuS semiconductor nanoparticles manufactured in the second embodiment (reaction temperatures 125°C, 150°C, and 165°C). Detailed Implementation

[0058] Implementation Method 1 The following describes embodiments of the present invention. In this embodiment, by adjusting the mixing ratio of Ag precursor and Au precursor, AgAuS-based compounds (Ag...) with various compositions were manufactured. (nx) Au (ny) S (nz) Semiconductor nanoparticles composed of [missing information]. The fabricated semiconductor nanoparticles were then subjected to TEM observation and XRD analysis to confirm the average particle size and crystal structure, followed by measurements of absorption and emission spectra. In this embodiment, Ag [missing information] was used. (nx) Au (ny) S (nz) An overview of the manufacturing process of semiconductor nanoparticles is as follows: Figure 1 As shown.

[0059] Weigh silver acetate (Ag(OAc)) as the Ag precursor and Au resinate (C) as the Au precursor. 10 H 18 Au2S2 (refer to the chemical formula below) and 0.2 mmol of thiourea as the S precursor are placed in a test tube, and then 100 ml of... 3 1-Dodecylthiol (DDT) as a protective agent and 2900mm 3 Oleylamine (OLA) is used as a solvent.

[0060] [Chemical Formula 1]

[0061]

[0062] In this embodiment, the total amount of silver acetate and Au resin salt was set to 0.4 mmol, and the atomic ratio of Ag:Au metal atoms (a:b) was adjusted. In this embodiment, Ag was synthesized using seven atomic ratios: a:b = 1.0:0, 0.78:0.22, 0.60:0.40, 0.45:0.55, 0.33:0.67, 0.14:0.86, and 0:1.0. (nx) Au (ny) S (nz) Compounds were then added to a test tube along with the precursors, protecting agents, solvents, and a stir bar. Three nitrogen replacements were performed, and the reaction temperature was set to 150°C using a heated stirrer, with stirring for 10 minutes. After the reaction was complete, the mixture was cooled for 30 minutes and then transferred to a small test tube. The mixture was then centrifuged at 4000 rpm for 5 minutes to separate the supernatant and precipitate.

[0063] Then, add 4000 mg of [unspecified substance] to the supernatant. 3 Methanol, used as a non-solvent, forms a precipitate, which is then centrifuged at 4000 rpm for 5 minutes to recover the precipitate. 4000 ml of [a specific solvent] is then added to the precipitate. 3 After dispersing the nanoparticles in ethanol, they were centrifuged under the same conditions to remove byproducts and solvent for purification. The resulting precipitate (semiconductor nanoparticles) was then dispersed in a 4000 nm medium. 3 In chloroform, AgAuS series compounds (Ag...) were obtained. (nx) Au (ny) S (nz) A dispersion of semiconductor nanoparticles was prepared. After nitrogen replacement, the dispersion was transferred to a sample vial, protected from light, and stored under cold.

[0064] [TEM observation and average particle size determination]

[0065] The manufactured semiconductor nanoparticles (a:b = 1.0:0, 0.78:0.22, 0.60:0.40, 0.45:0.55, 0.33:0.67, 0.14:0.86, 0:1.0) were observed by TEM. Figure 2 TEM images of the semiconductor nanoparticles fabricated in this embodiment are shown (magnification referenced to the scale bar of each photograph (10 nm)). The TEM images confirm the synthesis of approximately spherical semiconductor nanoparticles.

[0066] Based on these TEM images, the average particle size of each component of the semiconductor nanoparticles was determined and calculated. In the particle size determination, the particle size was calculated for all measurable semiconductor nanoparticles included in the TEM images, and the average particle size and standard deviation were calculated. The results are as follows: Figure 3As shown. The error bars in each graph represent the standard deviation. According to... Figure 3 In this embodiment, the average particle size of the semiconductor nanoparticles produced is in the range of 2 nm to 5 nm. Regarding the Ag:Au ratio, the particle size of particles with a:b = 0:1 (Au₂S) tends to be smaller; otherwise, there is no significant difference.

[0067] Compositional Analysis of Semiconductor Nanoparticles

[0068] ICP analysis was performed in conjunction with the TEM observations described above to analyze the composition of the semiconductor nanoparticle samples. In the ICP analysis, an Agilent 5110 measuring instrument manufactured by Agilent Technologies Inc. was used. After pretreatment using microwave acid decomposition, measurements were performed at an RF power of 1.2 kW, a plasma gas flow rate of 12 L / min, and an auxiliary gas flow rate of 1.0 L / min. The analytical results for seven types of semiconductor nanoparticles with Ag / Au atomic ratios (a:b) of a:b = 1.0:0, 0.78:0.22, 0.60:0.40, 0.45:0.55, 0.33:0.67, 0.14:0.86, and 0:1.0 are shown in Table 1. As can be seen from Table 1, although the atomic ratios (x:y:z) of the semiconductor nanoparticles manufactured in this embodiment are not exactly the same as the atomic ratios (a:b) of the metal precursors, they are close values. The cation / anion ratio ((x+y) / (2z)) shows a value of 0.78 to 0.95, indicating semiconductor particles composed of a non-stoichiometric composition lacking cations. It should be noted that in the semiconductor nanoparticles synthesized in this embodiment, the total concentration of Ag, Au, and S in the AgAuS compound is 100% by mass.

[0069] [Table 1]

[0070]

[0071] [XRD Analysis]

[0072] XRD analysis was performed on each semiconductor nanoparticle. The XRD analysis apparatus was an Ultima IV manufactured by Rigaku Corporation, with the characteristic X-rays set to CuKα rays and the analysis conditions set to 1° / min. Figure 4 The diffraction patterns of the seven types of nanoparticles manufactured in this embodiment are shown. Furthermore, Figures 5a-5c This image shows magnified diffraction patterns of three nanoparticles with Ag and Au atomic ratios (a:b) of 0:1.0, 0.60:0.40, and 0:1.0. Based on... Figure 5cIn semiconductor nanoparticles with an atomic ratio of 0:1.0, peaks consistent with the diffraction pattern of Au₂S were obtained. Furthermore, according to... Figure 5a In semiconductor nanoparticles with an atomic ratio of 1.0:0, although some peaks on the high-angle side were inconsistent, peaks from the diffraction of Ag₂S near 35–37 °C were observed. On the other hand, referring to… Figure 5b In semiconductor nanoparticles with an atomic ratio of 0.60:0.40, in addition to the peak from Ag3AuS2, peaks from Ag were also observed. 1.43 Au 0.66 The peak of S. Therefore, it is inferred that, according to Table 1, the overall composition of the compound for this semiconductor nanoparticle is Ag. n(0.68) Au n(0.32) S n(0.6) (x = 0.68, y = 0.32, z = 0.60), but may be composed of Ag3AuS2 and Ag 1.43 Au 0.66 It is composed of a mixed phase of S.

[0073] Then, refer to Figure 4 In semiconductor nanoparticles with metal ratios (Ag:Au)a:b = 0.78:0.22, 0.60:0.40, 0.45:0.55, 0.33:0.67, and 0.14:0.86, it was confirmed that as the Ag ratio increased and the Au ratio decreased, the peak mode gradually shifted from Au₂S to Ag₂S. Based on the XRD analysis of this embodiment, although the structure / composition of the solid solution of the particles synthesized with each atomic ratio has not yet been determined, or the composition and quantity of the mixture when coexisting, it can be confirmed that crystalline particles can be synthesized in any composition.

[0074] [Determination of absorption and emission spectra]

[0075] Next, the absorption and emission spectra of each semiconductor nanoparticle were measured. Absorption spectra were measured using a UV-Vis spectrophotometer (Agilent Technologies Inc., Agilent 8453), with the wavelength range set to 400 nm to 1100 nm. The measurement results of the absorption spectra of the semiconductor nanoparticles in this embodiment are as follows: Figure 6 As shown.

[0076] The emission spectra were measured using a fluorescence spectrophotometer (Hamamatsu Photonics KK, PMA-12) with the excitation wavelength set to 365 nm. The sample absorbance at 365 nm was adjusted to 0.1 using chloroform solution (n = 1.4429) for measurement.

[0077] In addition, an absolute PL quantum yield apparatus (Hamamatsu Photonics KK, C9920-03) was used in the determination of the luminescence quantum yield. When luminescence was observed at wavelengths above 1000 nm, the emission spectra were measured using a multi-channel spectrophotometer (Hamamatsu Photonics KK, PMA-12 (models: C10027-02 (wavelength range 350–1100 nm) and 10028-01 (wavelength range 900–1650 nm)). The sample absorbance at 700 nm was adjusted to 0.1 using chloroform solution (n = 1.4429) for measurement. The excitation wavelength was set to 700 nm, and measurements were performed. Regarding the calculation of the luminescence quantum yield, for the emission spectra obtained using a fluorescence spectrophotometer, the emission spectrum of an ethanol solution (n = 1.3618) of indocyanine green (ICG: Φ ​​= 13.2%), a near-infrared luminescent organic fluorescent pigment, was measured as a standard sample, and the luminescence quantum yield of each sample was calculated using the following formula via a relative method.

[0078] [Mathematical Expression 1]

[0079]

[0080] (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)

[0081] Figure 7 and Figure 8 The emission spectrum of the semiconductor nanoparticles of this embodiment, as measured and calculated above, is shown. Furthermore, Figure 9 Showing from Figure 6 The relationship between the atomic ratio a:b of the semiconductor nanoparticles obtained in this embodiment and the wavelength at the long-wavelength absorption end is shown. Additionally, Figure 10 Showing from Figure 7 and Figure 8 The relationship between the atomic ratio a:b of the semiconductor nanoparticles obtained in this embodiment and the luminescence quantum yield.

[0082] according to Figure 9 In semiconductor nanoparticles with a:b = 1.0:0 (Ag₂S) and 0.78:0.22, the absorption wavelength reaches a long wavelength region above 1100 nm, which cannot be accurately measured. The absorption wavelength temporarily shifts towards shorter wavelengths as the Ag ratio decreases compared to a:b = 0.78:0.22, reaching its shortest wavelength (660 nm) at a:b = 0.45:0.55. When the Ag ratio decreases further, the absorption wavelength shifts towards longer wavelengths again, and is estimated to be 970 nm in particles with a:b = 0:1.0 (Au₂S). The Ag₂S content of this invention...(nx) Au (ny) S (nz) In the semiconductor nanoparticles that were formed, the absorption wavelength was confirmed to be above 600 nm.

[0083] In addition, from Figure 10 It can be seen that the luminescence quantum yield of the semiconductor nanoparticles in this embodiment reaches its maximum near the atomic ratio a:b = 0.60:0.40. In the Ag of the present invention... (nx) Au (ny) S (nz) Among the semiconductor nanoparticles, when a:b = 1.0:0 or 0:1.0 is used as a reference example (Ag₂S or Au₂S), nanoparticles synthesized with a:b = 0.33:0.67 to 0.78:0.22 are considered particularly suitable. Furthermore, according to Table 1, in semiconductor nanoparticles manufactured with the aforementioned suitable atomic ratios, the atomic ratio (x, y) of Ag and Au is x / (x+y) of 0.46 to 0.78, i.e., x / y is 0.85 to 3.5.

[0084] Implementation Method 2 In this embodiment, silver acetate and gold resin salts are used to fix the atomic ratio (a:b) of metal atoms at 0.60:0.40, while the reaction temperature during synthesis is varied to produce a product composed of Ag... (nx) Au (ny) S (nz) Semiconductor nanoparticles composed of compounds were analyzed, and their average particle size, absorption spectrum, and emission spectrum were determined. Ag (nx) Au (ny) S (nz) The manufacturing process for semiconductor nanoparticles is essentially the same as in the first embodiment. Figure 1 In this study, the total amount of silver acetate and Au resin salt was set to 0.4 mmol, and the atomic ratio of their respective metal inputs (a:b) was set to 0.60:0.40, thus forming a reaction system. Then, semiconductor nanoparticles were manufactured by setting the reaction temperature to five different conditions: 100℃, 125℃, 150℃, 165℃, and 175℃.

[0085] [ [TEM observation and determination of average particle size]

[0086] For the semiconductor nanoparticles manufactured at each reaction temperature, TEM observation was performed in the same manner as in the first embodiment. Figure 11 TEM images of the various semiconductor nanoparticles are shown. According to... Figure 11 In this embodiment, the generation of approximately spherical nanoparticles was also confirmed. Furthermore, Figure 12The relationship between reaction temperature and the average particle size measured for each semiconductor nanoparticle is shown. It can be seen that the particle size of the semiconductor nanoparticles increases with increasing reaction temperature. This is believed to be because the increase in reaction temperature promotes crystal growth.

[0087] [Determination of absorption and emission spectra]

[0088] Absorption and emission spectra were measured for each semiconductor nanoparticle. These measurement methods were the same as those in Embodiment 1.

[0089] Figure 13 The results of the absorption spectrum measurements of the semiconductor nanoparticles of this embodiment are shown. Additionally, Figure 14 This shows the relationship between the reaction temperature and the wavelength at the longer absorption end, obtained from absorption spectroscopy measurements. Based on... Figure 14 Even if the reaction temperature changes, the absorption wavelength of the semiconductor nanoparticles is not significantly affected, remaining approximately constant at 650–750 nm. In the semiconductor nanoparticles manufactured in this embodiment, absorption wavelengths above 600 nm were also confirmed.

[0090] in addition, Figure 15 The emission spectrum of the semiconductor nanoparticles of this embodiment is shown. From Figure 15 It can be seen that within the reaction temperature range of 100–165℃, the emission peak wavelength of the semiconductor nanoparticles is 700–800 nm, which remains almost unchanged. No emission peak was detected at 175℃. Figure 16 This illustrates the relationship between the reaction temperature and the luminescence quantum yield of the semiconductor nanoparticles in this embodiment. According to... Figure 16 Up to 100℃ to 150℃, the luminescence quantum yield of the obtained semiconductor nanoparticles increases with increasing reaction temperature. On the other hand, when the reaction temperature is further increased to 165℃ and 175℃, the luminescence quantum yield of the obtained semiconductor nanoparticles decreases.

[0091] [XRD Analysis]

[0092] Furthermore, XRD analysis was performed on the semiconductor nanoparticles obtained by setting the reaction temperature to 125°C, 150°C, and 165°C. The analysis conditions were the same as in the first embodiment. Figure 17 The diffraction patterns of each semiconductor nanoparticle are shown. From Figure 17It is evident that the diffraction peaks of the semiconductor nanoparticles manufactured at 165°C become sharper, thus exhibiting higher crystallinity. When considering the results of the aforementioned average particle size measurements, it is shown that the increased crystal growth due to the rising reaction temperature enhances both the particle size and crystallinity of the semiconductor nanoparticles. Therefore, it can be concluded that while the reaction temperature for the semiconductor nanoparticles of this invention can be between 100°C and 175°C, from the viewpoint of luminescence quantum yield, a reaction temperature below 165°C is more suitable.

[0093] Industrial applicability

[0094] As explained above, the semiconductor nanoparticles of the present invention, composed of AgAuS-based compounds and having a novel composition, exhibit excellent optical properties. Furthermore, AgAuS-based compounds are low-toxicity compounds with biocompatibility. The semiconductor nanoparticles of the present invention are expected to be used in light-emitting elements, fluorescent materials, or photoelectric conversion elements or light-receiving elements mounted on solar cells or light sensors, etc., in display devices or as labeling materials for detecting biological substances.

[0095] Furthermore, based on this invention, semiconductor nanoparticles capable of exhibiting emission / absorption properties in the near-infrared region can also be obtained. In recent years, as photoelectric conversion elements with high responsiveness in the near-infrared region, light-receiving elements suitable for LIDAR (Light Detection and Ranging) or near-infrared (SWIR) image sensors have emerged. The semiconductor nanoparticles of this invention are expected to be used in photoelectric conversion elements operating in such a near-infrared region.

Claims

1. A semiconductor nanoparticle, which is a semiconductor nanoparticle composed of a semiconductor crystal containing Ag, Au, and S as essential constituent elements. The compound is of the general formula Ag. (nx) Au (ny) S (nz) It indicates that it is a ternary compound of AgAuS with monovalent Ag, monovalent Au, and S. Here, in the general formula, n is any positive integer, x, y, and z represent the proportion of the number of each atom of Ag, Au, and S in the compound, are real numbers of 0 < x, y, z ≤ 1, and x / y is more than 1 / 7 and less than 7, and (x+y) / 2z is 0.79 to 0.

95.

2. The semiconductor nanoparticles according to claim 1, wherein, The value of x / (x+y) is a real number greater than 0.33 and less than 0.

78.

3. The semiconductor nanoparticles according to claim 1 or claim 2, wherein, The average particle size is between 2 nm and 20 nm.

4. The semiconductor nanoparticles according to claim 1 or claim 2, Its surface is bonded with at least one of the following as a protective agent: alkylamine with 4 to 20 carbon atoms in the alkyl chain, alkenylamine with 4 to 20 carbon atoms in the alkenyl chain, alkylcarboxylic acid with 3 to 20 carbon atoms in the alkyl chain, alkenylcarboxylic acid with 3 to 20 carbon atoms in the alkenyl chain, alkylthiol with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphine with 4 to 20 carbon atoms in the alkyl chain, trialkylphosphine oxide with 4 to 20 carbon atoms in the alkyl chain, triphenylphosphine, and triphenylphosphine oxide.

5. The semiconductor nanoparticles according to claim 1 or claim 2, wherein, The long-wavelength absorption end of the absorption spectrum has a wavelength of 600 nm or more.

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