Semiconductor nanoparticles composed of AgAuS-based multicomponent compound

Abstract

The present invention relates to a semiconductor nanoparticle composed of a compound containing Ag, Au, S and a metal M as essential constitutional elements. In the present invention, the metal M is at least any of Al, Ga, In, Tl, Zn, Cd, Hg and Cu, and the compound has a total content of Ag, Au, S and the metal M of 95 mass % or more. In addition, a ratio (x/(x+y)) of the number of atoms of Ag to a sum of the number of atoms of Ag, x, and the number of atoms of Au, y, in the AgAuS-based multicomponent compound is preferably 0.50 or more and 0.88 or less. The semiconductor nanoparticle of the present invention has appropriate emission and extinction characteristics and is biocompatible.

Claims

1. A semiconductor nanoparticle comprising: a compound containing Ag, Au, S and a metal M as essential constitutional elements, wherein the metal M is at least any of Al, Ga, In, Tl, Zn, Cd, Hg and Cu, the compound has a total content of Ag, Au, S and the metal M of 95 mass % or more, and a ratio (x/(x+y)) of the number of atoms of Ag to a sum of the number of atoms of Ag, x, and the number of atoms of Au, y, in the compound is 0.60 or more and 0.88 or less.

2. The semiconductor nanoparticle according to claim 1, wherein a content of the metal M in the compound is 1 at % or more and 40 at % or less.

3. The semiconductor nanoparticle according to claim 1, wherein a content of S in the compound is 30 at % or more and 60 at % or less.

4. The semiconductor nanoparticle according to claim 1, wherein the compound is one containing Ag, Au and S in which the metal M is doped.

5. A semiconductor nanoparticle comprising: a compound containing Ag, Au, S and a metal M as essential constitutional elements, wherein the compound comprises: a core compound containing Ag, Au and S; a shell compound that coats at least a part of a surface of the core compound and contains the metal M and/or essentially contains the metal M and contains at least any of Ag, Au and S, and a ratio (x/(x+y)) of the number of atoms of Ag to a sum of the number of atoms of Ag, x, and the number of atoms of Au, y, in the compound is 0.60 or more and 0.88 or less.

6. The semiconductor nanoparticle according to claim 1, having an average particle diameter of 2 nm or more and 20 nm or less.

7. The semiconductor nanoparticle according to claim 1, having at least any of an alkylamine having 4 to 20 carbon atoms in an alkyl chain, an alkenylamine having 4 to 20 carbon atoms in an alkenyl chain, an alkylcarboxylic acid having 3 to 20 carbon atoms in an alkyl chain, an alkenylcarboxylic acid having 3 to 20 carbon atoms in an alkenyl chain, an alkanethiol having 4 to 20 carbon atoms in an alkyl chain, a trialkylphosphine having 4 to 20 carbon atoms in an alkyl chain, a trialkylphosphine oxide having 4 to 20 carbon atoms in an alkyl chain, triphenylphosphine and triphenylphosphine oxide as a protective agent bonded to a surface thereof.

8. The semiconductor nanoparticle according to claim 1, wherein a long wavelength-side absorption edge wavelength of an absorption spectrum is 600 nm or higher.

9. The semiconductor nanoparticle according to claim 2, wherein a content of S in the compound is 30 at % or more and 60 at % or less.

10. The semiconductor nanoparticle according to claim 2, wherein the compound is one containing Ag, Au and S in which the metal M is doped.

11. The semiconductor nanoparticle according to claim 3, wherein the compound is one containing Ag, Au and S in which the metal M is doped.

12. The semiconductor nanoparticle according to claim 2, wherein the compound comprises a core compound containing Ag, Au and S; and a shell compound that coats at least a part of a surface of the core compound and contains the metal M and/or essentially contains the metal M and contains at least any of Ag, Au and S.

13. The semiconductor nanoparticle according to claim 3, wherein the compound comprises a core compound containing Ag, Au and S; and a shell compound that coats at least a part of a surface of the core compound and contains the metal M and/or essentially contains the metal M and contains at least any of Ag, Au and S.

14. The semiconductor nanoparticle according to claim 2, having an average particle diameter of 2 nm or more and 20 nm or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view showing the outline of steps for producing a nanoparticle of a AgAuS ternary compound;

(2) FIG. 2 is TEM images of semiconductor nanoparticles of AgAuS ternary compounds produced in a preliminary study;

(3) FIG. 3 is measurement results of absorption spectra of the nanoparticles produced in the preliminary study;

(4) FIG. 4 is measurement results of emission spectra and emission quantum efficiencies of the nanoparticles produced in the preliminary study;

(5) FIG. 5 is TEM images of In-added AgAuS-based multicomponent compound particles produced in First Embodiment;

(6) FIG. 6 is measurement results of absorption spectra of the In-added AgAuS-based multicomponent compound particles produced in First Embodiment;

(7) FIG. 7 is measurement results of emission spectra and emission quantum efficiencies of the In-added AgAuS-based multicomponent compound particles produced in First Embodiment;

(8) FIG. 8 is TEM images of In-added AgAuS-based multicomponent compound particles produced in Second Embodiment;

(9) FIG. 9 is XRD diffraction profiles of the In-added AgAuS-based multicomponent compound particles produced in Second Embodiment;

(10) FIG. 10 is TEM images and HAADF images of the In-added AgAuS-based multicomponent compound particles produced in Second Embodiment;

(11) FIG. 11 is an example of the result of an EDX analysis of a vicinity of a center and a vicinity of a surface layer of a AgAuS ternary compound particle to which In is not added;

(12) FIG. 12 is an example of the results of EDX analyses of a vicinity of a center and a vicinity of a surface layer of an In-added AgAuS-based multicomponent compound particle;

(13) FIG. 13 is measurement results of absorption spectra of the In-added AgAuS-based multicomponent compound particles produced in Second Embodiment;

(14) FIG. 14 is measurement results of emission spectra and emission quantum efficiencies of the In-added AgAuS-based multicomponent compound particles produced in Second Embodiment;

(15) FIG. 15 is TEM images of Cu-added AgAuS-based multicomponent compound nanoparticles produced in Third Embodiment;

(16) FIG. 16 is measurement results of absorption spectra and emission spectra of the Cu-added AgAuS-based multicomponent compounds produced in Third Embodiment;

(17) FIG. 17 is TEM images of Zn-added AgAuS-based multicomponent compound nanoparticles produced in Fourth Embodiment; and

(18) FIG. 18 is measurement results of absorption spectra and emission spectra of the Zn-added AgAuS-based multicomponent compounds produced in Fourth Embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(19) Hereinafter, embodiments of the present invention will be described. In the present embodiments, first, as a preliminary study, semiconductor nanoparticles composed of AgAuS ternary compounds having a variety of compositions were produced with the mixing ratio between a Ag precursor and a Au precursor adjusted. In addition, regarding the produced semiconductor nanoparticles, TEM observation and composition analyses were performed, and then,

(20) [Production of AgAuS Ternary Compound Nanoparticle]

(21) FIG. 1 is a view showing the outline of steps for producing a nanoparticle of a AgAuS ternary compound. As raw materials, silver acetate (Ag(OAc)) as the Ag precursor, chloro(dimethyl sulfide) gold (I) as the Au precursor and thiourea as a S precursor were weighed and put into a test tube, and furthermore, 0.1 cm.sup.3 of 1-dodecanethiol (DDT) as a protective agent and 2.9 cm.sup.3 of oleylamine (OLA) as a solvent were added thereto.

(22) In this preliminary study, the metal atom charged atomic ratio (Ag:Au=a:b provided that a+b=1.0) of Ag to Au was adjusted while the total amount of Ag and Au, which were the metal atoms contained in the precursors, was maintained at 0.4 mmol. The amount of the thiourea was commonly set to 0.2 mmol. Here, AgAuS ternary compounds were synthesized with seven charged atomic ratios in which the charged ratios of Ag were set to 1.0, 0.88, 0.75, 0.63, 0.5, 0.25 and 0.

(23) Each precursor, the protective agent, the solvent and a stirrer were put into the test tube, substituted with nitrogen three times, and then heated and stirred with a hot stirrer for 10 minutes at a reaction temperature set to 150 C. After the end of a reaction, the components were left to stand for 30 minutes until cool and then transferred to a small test tube, centrifugation was performed at 4000 rpm for five minutes, and a supernatant and a precipitate were separated.

(24) Subsequently, 4 cm.sup.3 of methanol was added to the supernatant as a nonsolvent to generate a precipitate, centrifugation was performed at 4000 rpm for five minutes, and the precipitate was collected. Furthermore, this precipitate was dispersed with 4 cm.sup.3 of ethanol added thereto, then, centrifugation was performed under the same conditions, and a by-product and the solvent were removed to purify the precipitate.

(25) The precipitate obtained by the above-described operation was dispersed in 3 cm.sup.3 of chloroform, thereby obtaining a dispersion liquid of the nanoparticle of the AgAuS ternary compound. This dispersion liquid was transferred to a sample bottle, substituted with nitrogen, shielded from light and stored in a refrigerator.

(26) [TEM Observation and Average Particle Diameter Measurement]

(27) On the nanoparticles of the produced AgAuS ternary compounds (the Ag charged ratios a=1.0, 0.88, 0.75, 0.63, 0.5, 0.25 and 0), TEM observation was performed. FIG. 2 shows the TEM images of the nanoparticles of the produced AgAuS ternary compounds (regarding magnifications, refer to a scale bar on each photograph). From each TEM image, it was confirmed that a substantially spherical nanoparticle was synthesized. In addition, based on the TEM image, the average particle diameter of the nanoparticle having each composition was measured and calculated. In the measurement of the particle diameters, particle diameters are obtained from all measurable nanoparticles in the TEM image, and the average particle diameter were calculated.

(28) [Composition Analysis of Nanoparticle]

(29) EDXanalysis was performed together with the above-described TEM observation, thereby analyzing the compositions of nanoparticle. The content of each element of Ag, Au and S in the seven nanoparticles in which the charged atomic ratios a of Ag were set to 1.0, 0.88, 0.75, 0.63, 0.5, 0.25 and 0 is shown in Table 1. The results of the composition analyses are displayed in at % with respect to the entire nanoparticle in this preliminary study and each embodiment to be described below. In addition, the ratios (x/(x+y)) of the number of Ag atoms to the sum of the number of Ag atoms (x) and the number of Au atoms (y) that are calculated based on the composition analysis results are also shown in Table 1.

(30) TABLE-US-00001 TABLE 1 Ag charged ratio Composition (at %) No. (a) Ag Au S x/(x + y) 1 0.00 0.00 40.3 59.7 0.00 2 0.25 21.9 33.2 44.9 0.40 3 0.50 35.6 23.6 40.9 0.60 4 0.63 41.6 17.9 40.4 0.70 5 0.75 47.8 12.3 39.9 0.80 6 0.88 51.8 7.9 40.3 0.87 7 1.00 61.9 0.00 38.1 1.00

(31) It is found from Table 1 that the proportions (x/(x+y)) of the number of atoms of Ag in the nanoparticles (AgAuS) produced in the preliminary study of the present embodiment do not completely match the Ag charged ratios (a) of the metal precursor, but are liable to become closer as the Ag charged ratio increases.

(32) [Measurement of Absorption Spectrum and Emission Spectrum]

(33) Next, for the nanoparticle of each AgAuS ternary compound, the absorption spectrum was measured. The absorption spectrum was measured with a UV-Visible spectrophotometer (manufactured by Agilent Technologies International Japan, Ltd., manufactured by Agilent 8453) within a wavelength range of 400 nm to 1100 nm.

(34) In addition, regarding each nanoparticle, an emission spectrum and an emission quantum efficiency were measured. For the emission spectrum, a diode array spectrophotometer (PMA-12, C10027-02) manufactured by Hamamatsu Photonics K.K. was used. The sample was adjusted in a chloroform solution (n=1.4429) so that the absorbance at 365 nm reached 0.1, and the measurement was performed.

(35) In addition, for the measurement of the emission quantum yield, an absolute PL quantum yield spectrometer (manufactured by Hamamatsu Photonics K.K., C9920-03) was used. In a case where emission was observed at a long wavelength of 1000 nm or longer, the emission spectrum was measured with a photonic multichannel analyzer (manufactured by Hamamatsu Photonics K.K., PMA-12 (model Nos.: C10027-02 (wavelength range: 350 to 1100 nm) and 10028-01 (wavelength range: 900 to 1650 nm)). During the measurement, the sample was adjusted in a chloroform solution (n=1.4429) so that the absorbance at 700 nm reached 0.1. The excitation light wavelength was set to 700 nm in the measurement. For the calculation of the emission quantum yield, regarding the emission spectrum measured with the fluorescence spectrophotometer, the emission spectrum of an ethanol solution (n=1.3618) of indocyanine green (ICG: =13.2%), which is a near-infrared emitting organic fluorescent dye, was measured as a standard specimen, and the emission quantum yield of each sample was calculated from the following expression by the comparative method.

(36) $\begin{array}{cc}{}_x={}_{\mathrm{st}}\left(\frac{{\mathrm{FA}}_x}{{\mathrm{FA}}_{\mathrm{st}}}\right)\left(\frac{A_{\mathrm{st}}}{A_x}\right)\left(\frac{I_{\mathrm{ex},\mathrm{st}}}{I_{\mathrm{ex},x}}\right)\left(\frac{n_x^2}{n_{\mathrm{st}}^2}\right)\left(A:\mathrm{Absorbance}\mathrm{of}\mathrm{specimen}\mathrm{at}\mathrm{excitation}\mathrm{wavelength},\mathrm{lex}:\mathrm{Intensity}\mathrm{of}\mathrm{excitation}\mathrm{light}\mathrm{at}\mathrm{excitation}\mathrm{wavelength},n:\mathrm{Refractive}\mathrm{index}\mathrm{of}\mathrm{solvent}\right)& \left[\mathrm{Expression}1\right]\end{array}$

(37) The measurement results of the absorption spectra of the AgAuS ternary compound nanoparticles produced in the preliminary study are shown in FIG. 3. In addition, the measurement results of the emission spectra and the emission quantum efficiencies are shown in FIG. 4. In addition, the relationship among the composition of each nanoparticle, the emission wavelength and the emission quantum efficiency is summarized and shown in Table 2.

(38) TABLE-US-00002 TABLE 2 Ag charged Composition (at %) PLQY No. ratio (a) Ag Au S x/ (x + y) (nm) (%) 1 0.00 0.00 40.3 59.7 0.00 0 2 0.25 21.9 33.2 44.9 0.40 850 1.9 3 0.50 35.6 23.6 40.9 0.60 740 5.3 4 0.63 41.6 17.9 40.4 0.70 770 5.3 5 0.75 47.8 12.3 39.9 0.80 778 4.2 6 0.88 51.8 7.9 40.3 0.87 818 4.8 7 1.00 61.9 0.00 38.1 1.00 1100 1.00

(39) Referring to FIG. 3, it is confirmed that the absorption edge wavelengths of the AgAuS ternary compound nanoparticles are all 600 nm or more. Referring further to FIG. 4 and Table 2, it is found that the AgAuS ternary compound nanoparticles all show emission. In addition, relatively high emission quantum efficiencies are exhibited in the nanoparticles having a charged ratio of Ag of more than 0.5 (x/(x+y)=0.6). In addition, it is found that, as the Ag charged ratio increases and the proportion (x/(x+y)) of the number of Ag atoms increases, the emission peak is liable to be shifted in the long wavelength direction (except when a=0.25).

(40) First Embodiment: From the above-described results of the preliminary study, it was confirmed that the nanoparticle composed of the AgAuS ternary compound is capable of exhibiting light-absorptive and light-emitting characteristics as an optical semiconductor material. Based on the results of this preliminary study, semiconductor nanoparticles were produced by adding In as a metal M to the AgAuS ternary compound nanoparticles produced above.

(41) In the present embodiment, In was added to the AgAuS ternary compound nanoparticles where the emission quantum efficiency was relatively high in the preliminary study and the Ag charged ratio was 0.5 or more (No. 3 to No. 6 in Table 1) and the AgS compound nanoparticle having a charged ratio of 1.0, which is for reference, (No. 7). In addition, the same number of atoms of In as the total number of atoms (x+y) of the number of atoms of Ag(x) and the number of atoms of Au (y) that configured the AgAuS ternary compound to which In was to be added were added to the reaction system (the amount of addition equal to the number of atoms of Ag and Au will be referred to as 1 equivalent).

(42) [Addition of Metal M (in) (1 Equivalent)]

(43) The AgAuS ternary compound nanoparticle produced above was fractionated such that the total metal amount of Ag and Au reached 1.2310.sup.5 mol and put into a test tube together with 1.2310.sup.5 mol of indium chloride (InCl.sub.3) and 1.8410.sup.5 mol (1.5 equivalents with respect to indium chloride) of thioacetamide, and furthermore, 3.0 cm.sup.3 of dehydrated oleylamine was put thereinto as a solvent. In addition, a reaction temperature was set to 110 C. with a hot stirrer, and the components were stirred while being heated for 15 minutes. After the end of a reaction, the components were left to stand for 20 minutes until cool and centrifuged to separate a supernatant and a precipitate. In addition, after the supernatant was separated and collected, an isolation and purification operation was performed in the same manner as in the preliminary study, thereby obtaining a semiconductor nanoparticle composed of the In-added AgAuS multicomponent compound of the present embodiment.

(44) [Variety of Studies of In-Added AgAuS Multicomponent Compound Nanoparticle]

(45) On the semiconductor nanoparticles composed of the In-added AgAuS multicomponent compounds produced above, TEM observation and composition analyses were performed in the same manner as in the preliminary study. A TEM image of each AgAuS-based multicomponent compound particle to which In was added is shown in FIG. 5, and the result of the composition analysis is shown in Table 3.

(46) TABLE-US-00003 TABLE 3 Ag charged Composition (at %) ratio (a) Ag Au S In x/ (x + y) Example 1 0.50 29.4 19.4 42.8 8.4 0.60 Example 2 0.63 36.4 14.6 40.9 8.1 0.71 Example 3 0.75 40.4 10.3 40.8 8.4 0.80 Example 4 0.88 44.6 6.8 40.5 5.1 0.87 Reference 1.00 55.7 0.0 36.5 7.8 1.00 Example

(47) In addition, on each semiconductor nanoparticle, an absorption spectrum, an emission spectrum and an emission quantum efficiency were measured. Methods for measuring these were the same as those in the above-described preliminary study. The measurement results of the absorption spectra of the semiconductor nanoparticles (Ag charged ratios: 0.5, 0.63, 0.75, 0.88 and 1.0) produced in the present embodiment are shown in FIG. 6, the measurement results of the emission spectra are shown in FIG. 7, and these are summarized and shown in Table 4.

(48) TABLE-US-00004 TABLE 4 Ag charged Composition (at %) x/ PLQY ratio (a) Ag Au S In (x + y) (nm) (%) Example 1 0.50 29.4 19.4 42.8 8.4 0.60 760 1.3 Example 2 0.63 36.4 14.6 40.9 8.1 0.71 774 26.8 Example 3 0.75 40.4 10.3 40.8 8.4 0.80 805 50.3 Example 4 0.88 44.6 6.8 40.5 5.1 0.87 885 22.3 Reference 1.00 55.7 0.0 36.5 7.8 1.00 0 Example

(49) From Table 4, clear increases in the emission quantum efficiencies by the addition of the metal M (In) to the AgAuS ternary compounds were confirmed. In addition, shifts of the emission spectra of the AgAuS ternary compounds in the long wavelength direction by the addition of In were confirmed. In Example 1 where the Ag charged ratio was 0.5, the emission quantum efficiency did not increase, but a shift of the emission spectrum toward the long wavelengths was observed.

(50) Second Embodiment: In the present embodiment, a relationship between the amount of In added to the AgAuS-based multicomponent compound nanoparticle and the optical semiconductor characteristics was studied. Here, In was added to a AgAuS ternary compound where the Ag charged ratio was 0.75. A method for adding In and reaction conditions were set in the same manner as in First Embodiment. Regarding the addition of In, indium chloride having the same number of atoms of In as the sum of the number of Ag atoms and the number of Au atoms in the nanoparticle (1.2310.sup.5 mol) was regarded as a standard (1 equivalent) in First Embodiment, and 0.25 equivalents (3.0810.sup.6 mol; Example 5), 0.5 equivalents (6.1510.sup.6 mol; Example 6), 2 equivalents (2.4610.sup.5 mol; Example 7) and 4 equivalents (4.92 10.sup.5 mol; Example 8) of indium chloride were added. In addition, together with indium chloride, 0.25 equivalents (4.0610.sup.6 mol; Example 5), 0.5 equivalents (9.2010.sup.6 mol; Example 6), 2 equivalents (3.68 10.sup.5 mol; Example 7) and 4 equivalents (7.3610.sup.5 mol; Example 8) of thioacetamide were added. These and the AgAuS ternary compound nanoparticle (the total metal amount of Ag and Au was 1.2310.sup.5 mol) were reacted with each other, thereby producing AgAuS-based multicomponent compound nanoparticles.

(51) In addition, regarding each semiconductor nanoparticle to which In had been added in each amount added, TEM observation and a composition analysis (SEM-EDS) were performed in the same manner as in First Embodiment. A TEM image of each semiconductor nanoparticle is shown in FIG. 8. In addition, the result of the composition analysis of each semiconductor nanoparticle (amount of In added: 0.25 equivalents, 0.5 equivalents, 1 equivalent, 2 equivalents or 4 equivalents) is shown in Table 5.

(52) TABLE-US-00005 TABLE 5 Amount In Composition (at %) added Ag Au S In x/ (x + y) Reference 0 equivalents 47.8 12.3 39.9 0.0 0.80 Example Example 5 0.25 equivalents 46.6 12.3 39.6 1.5 0.79 Example 6 0.5 equivalents 43.3 11.0 39.7 6.0 0.80 Example 3 1 equivalents 40.4 10.3 40.8 8.4 0.80 Example 7 2 equivalents 29.7 7.2 46.4 16.7 0.80 Example 8 4 equivalents 23.6 6.0 49.9 20.5 0.80

(53) It is found from Table 5 that the content of In in the semiconductor nanoparticle increases as the amount of In added increases.

(54) Next, in order to study the details of the configurations of the semiconductor nanoparticles, XRD analyses and observation with HAADF-STEM were performed on the nanoparticles in which the amount of In added was 0 equivalents, 1 equivalent, 2 equivalents and 4 equivalents (Reference Example and Examples 3, 7 and 8) An XRD analyzer was Ultima IV produced by Rigaku Corporation, CuK rays were used as characteristic X rays, and 1/min. was set as an analysis condition. A HAADF-STEM device was Tecnai Osiris produced by FEI Company, and as an analysis condition, the observation was performed at an accelerating voltage of 200 kV. In the HAADF-STEM observation, point analyses were performed with an EDX device attached to the device on the vicinity of the center and the vicinity of the surface layer of the nanoparticle. As the results of these analyses, the result of the XRD analysis of each semiconductor nanoparticle is shown in FIG. 9, and HAADF images and mapping images are shown in FIG. 10.

(55) Referring to the results of the XRD analyses in FIG. 9, it is noted as the amount of In added becomes 2 equivalents and 4 equivalents, the diffraction peak of AgInS.sub.2 in the vicinity of 27 increases. In addition, EDX point analyses were performed on the semiconductor nanoparticles observed with the HAADF-STEM, and examples of the results of performing the configuration ratio of each element in the vicinity of the center and in the vicinity of the surface layer are shown in FIGS. 11 and 12. Referring to the results of these EDX point analyses, it is considered that a AgAuS ternary compound particle to which In was not added (0 equivalents: Reference Example) contained Ag as a main component of the surface layer and had a core-shell structure in which the center was composed of the AgAuS ternary compound. This AgAuS ternary compound to which In was not added and the AgAuS-based multicomponent compound in which the amount of In added was 1 equivalent (Example 3) have similar configurations in the surface layer portions and contain no Au. In addition, it is confirmed that, as the amount of In added increases from 2 equivalents, Au in the surface layer portion increases.

(56) Therefore, ICP analyses were performed to more strictly estimate the composition (element ratio) and structure of each semiconductor nanoparticle. The ICP analysis was performed using Agilent 5110 manufactured by Agilent Technologies International Japan, Ltd. as a measuring instrument by performing a pretreatment by a microwave acid digestion method and then performing measurement at a 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 results of the composition analysis of each semiconductor nanoparticle by this ICP are shown in Table 6.

(57) TABLE-US-00006 TABLE 6 Amount of In Composition (atomic ratio)*.sup.1 added Ag Au S In Reference 0 equivalents 1.0 0.27 0.62 0.00 Example Example 3 1 equivalents 1.0 0.27 0.62 0.23 Example 7 2 equivalents 1.0 0.25 0.82 0.67 Example 8 4 equivalents 1.0 0.26 1.50 1.04 *.sup.1Relative value for which the number of Ag atoms is regarded as 1.0.

(58) In Table 6, regarding each nanoparticle, the composition is shown with ratios for which the number of atoms of Ag was regarded as 1.0. Table 6 shows that, when In was added to the AgAuS ternary compound particle, the S content rates of the AgAuS-based multicomponent compound particles in which the amounts of In added were 0 equivalents (In was not added) and 1 equivalent (Example 3 in First Embodiment), respectively, are almost the same. That is, it is considered that, until the addition of 1 equivalent, only In was added to the AgAuS ternary compound particle. In addition, it is considered that, as the amount of In added increases from 2 equivalents, the S content rate increases. When the results of FIGS. 11 and 12 above are collectively considered, it is assumed that, in the AgAuS-based multicomponent compound nanoparticles obtained by adding the metal M to the AgAuS ternary compound nanoparticle, there are cases where a structural change is caused due to the amount of the metal M added or the like. When the results of the evaluation of following optical semiconductor characteristics are taken into account, it is deemed that, regarding AgAuS-based multicomponent nanoparticles, there is no need to interpret a preferable structure in a limited manner.

(59) [Measurement of Optical Semiconductor Characteristics of AgAuS-Based Multicomponent Compound]

(60) After the above-described analyses were performed, regarding each semiconductor nanoparticle, the absorption spectrum, the emission spectrum and the emission quantum efficiency were measured in the same manner as in First Embodiment. These results are shown in FIG. 13, FIG. 14 and Table 7.

(61) TABLE-US-00007 TABLE 7 Amount of In Composition (at %) PLQY added Ag Au S In x/ (x + y) (nm) (%) Reference 0 equivalents 47.8 12.3 39.9 0.80 778 4.2 Example Example 5 0.25 equivalents 46.6 12.3 39.6 1.5 0.79 794 7.7 Example 6 0.5 equivalents 43.3 11.0 39.7 6.0 0.80 814 24.0 Example 3 1 equivalents 40.4 10.3 40.8 8.4 0.80 805 50.3 Example 7 2 equivalents 29.7 7.2 46.4 16.7 0.80 770 41.1 Example 8 4 equivalents 23.6 6.0 49.9 20.5 0.80 760 14.5

(62) FIG. 13 shows that there is no significant differences in the absorption spectra of the In-added AgAuS-based multicomponent compound nanoparticles due to the amount of In added. Referring to FIG. 14, the emission quantum efficiency exhibits the maximum value in the particle in which the amount of In added was 1 equivalent (First Embodiment). The emission quantum efficiency decreases as the amount of In added increases, but is the same as that of the AgAuS ternary compound particle to which In was not added. In addition, the emission spectra show that, in the particle in which the amount of In added was 1 equivalent, the peak was shifted in the long wavelength direction with respect to the AgAuS ternary compound particle to which In was not added, but the peak was shifted in the short wavelength direction with 2 equivalents and 4 equivalents. The decreases in the emission quantum efficiencies or the peak shifts toward the lower wavelengths of the emission spectra of these AgAuS-based multicomponent compound nanoparticles in which the amount of In added exceeded 1 equivalent are considered to arise from the advancement of the generation of the above-described AgInS.sub.2.

(63) Third Embodiment: In the present embodiment, AgAuS-based multicomponent compound nanoparticles were produced with Cu added to a AgAuS ternary compound particle. Cu was added to the AgAuS ternary compound in which the Ag charged ratio was 0.75 in First Embodiment.

(64) Regarding the addition of Cu, CuCl (copper chloride) was used as a Cu source, and copper chloride and thioacetamide were added to the AgAuS ternary compound particle in a solvent basically in the same manner as in First Embodiment. Regarding the amount of Cu added to the AgAuS ternary compound nanoparticle (the total metal amount of Ag and Au was 1.23 10.sup.5 mol), copper chloride having the same number of atoms of Cu as the sum of the number of Ag atoms and the number of Au atoms in the nanoparticle (1.2310.sup.5 mol) was regarded as a standard (1 equivalent), and the AgAuS ternary compound particle was reacted with 2 equivalents (2.4610.sup.5 mol) and 3 equivalents (3.6910.sup.5 mol) of copper chloride. In addition, in these reactions, together with copper chloride, 1 equivalent (6.1510.sup.6 mol), 2 equivalents (12.3 10.sup.6 mol) and 3 equivalents (18.45 10.sup.6 mol) of thioacetamide were added. Reaction conditions were set in the same manner as in First Embodiment.

(65) In addition, regarding the produced Cu-added AgAuS-based multicomponent compound nanoparticles, TEM observation and composition analyses were performed, and the absorption spectra and the emission spectra were then measured. The TEM observation results of the Cu-added AgAuS-based multicomponent compound nanoparticles of the present embodiment are shown in FIG. 15, and the results of the composition analyses are shown in Table 8. In addition, the measurement results of the absorption spectra and the emission spectra are shown in FIG. 16.

(66) TABLE-US-00008 TABLE 8 Composition (at %) Amount of Cu added Ag Au S Cu x/(x + y) 0 equivalents 47.8 12.3 39.9 0.0 0.80 1 equivalents 46.1 12.1 38.6 3.2 0.79 2 equivalents 42.9 11.2 38.7 7.2 0.79 3 equivalents 43.1 10.9 34.8 11.2 0.80

(67) From the Cu-added AgAuS-based multicomponent compound nanoparticles as well, it was observed increases in the Cu concentration in association with the increases in the amounts added. In addition, from the measurement results of the absorption spectra, it is confirmed that there are no significant changes in the absorption edge wavelengths, but changes in the spectrum shapes caused by the addition of Cu are observed, from which a possibility of characteristic adjustment by the addition of Cu is confirmed. From the Cu-added AgAuS-based multicomponent compound nanoparticles, no emission was confirmed.

(68) Fourth Embodiment: In the present embodiment, AgAuS-based multicomponent compound nanoparticles were produced with Zn added to a AgAuS ternary compound particle. Zn was added to the AgAuS ternary compound in which the Ag charged ratio was 0.75 in First Embodiment.

(69) Regarding the addition of Zn, Zn(C.sub.18H.sub.35O.sub.2).sub.2 (zinc stearate) was used as a Cu source, and zinc stearate and thioacetamide were added to the AgAuS ternary compound particle in a solvent basically in the same manner as in First Embodiment. Regarding the amount of Zn added, 0.510.sup.7 mol (particle) of the AgAuS ternary compound nanoparticle, 0.035 mmol of zinc stearate and 0.035 mmol of thioacetamide were reacted with one another such that a 1 nm-thick shell was formed on the surface of the AgAuS ternary compound particle. As reaction conditions, the components were heated at a temperature of 100 C. for one hour.

(70) Regarding the AgAuS-based multicomponent compound nanoparticles produced in the present embodiment, TEM observation and composition analyses were performed, and the absorption spectra and the emission spectra were then measured. The TEM observation results of the AgAuS-based multicomponent compound nanoparticles of the present embodiment are shown in FIG. 17, and the results of the composition analyses are shown in Table 9. In addition, the measurement results of the absorption spectra and the emission spectra are shown in FIG. 18.

(71) TABLE-US-00009 TABLE 9 Composition (at %) Zn addition Ag Au S Zn x/(x + y) No 47.8 12.3 39.9 0.0 0.80 Yes 19.9 5.7 39.7 34.7 0.78

(72) From the Zn-added AgAuS-based multicomponent compound nanoparticles of the present embodiment, emission was confirmed, but the emission quantum efficiencies were almost the same as those of the AgAuS ternary compound particles before the addition. From the Zn-added AgAuS-based multicomponent compound nanoparticles, however, peak shifts of the emission spectra in the long wavelength direction were confirmed, and a possibility of adjustment of emission characteristic was confirmed.

INDUSTRIAL APPLICABILITY

(73) As described above, the semiconductor nanoparticle composed of the novel AgAuS-based multicomponent compound of the present invention is capable of exhibiting favorable optical semiconductor characteristics. In addition, this AgAuS-based multicomponent compound is a low-toxic biocompatible compound. Accordingly, the semiconductor nanoparticle of the present invention is expected to be applied to light-emitting elements and fluorescent substances that are used for display devices, marker substances for detecting bio-related substances and the like or photoelectric conversion elements or light-receiving elements, which are mounted in solar cells, light sensors and the like.

(74) In addition, the semiconductor nanoparticle of the present invention is aimed at improving light-emitting and light-absorptive characteristics in the near-infrared range. This fact makes the present invention also useful for light receiving elements adapted for LIDAR or SWIR image sensors for which responsiveness in the near-infrared range has been emphasized among the above-described photoelectric conversion elements.