Phosphor, its manufacturing method, and light-emitting device using same

Abstract

To provide a method for manufacturing a carbon nanoparticle phosphor with adjusted chromaticity, the carbon nanoparticle phosphor obtained thereby, and a light-emitting device therewith.SOLUTION: A method for manufacturing a carbon nanoparticle phosphor of the present invention includes preparing a raw material solution in which at least a carbon source is dissolved in an organic solvent, and heating the raw material solution. The carbon nanoparticle phosphor of the present invention contains carbon element, oxygen element, nitrogen element, and hydrogen element, and contains amorphous carbon and graphitic carbon, and the nitrogen element includes pyridine nitrogen, amide nitrogen, pyrrole nitrogen, and a graphite nitrogen.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a phosphor, a method for producing the same, and a light-emitting device using the same. More particularly, the present invention relates to a phosphor using carbon nanoparticles, a method for producing the same, and a light-emitting device using the same. [Background technology]

[0002] In recent years, a composition containing a carbon nanoparticle phosphor that emits blue to red light upon irradiation with excitation light has been developed (see, for example, Patent Document 1). Patent Document 1 provides a composition containing a carbon nanoparticle phosphor that emits blue to red light upon irradiation with excitation light, using a method including the steps of: hydrothermally synthesizing a solution in which an organic substance selected from the group consisting of citric acid, benzoic acid, glucose, fructose, and sucrose, amines, and one or more selected from inorganic acids and acetic acid are dissolved in an aqueous solvent; adding alcohol to the solution obtained by the hydrothermal synthesis step and stirring; and extracting the supernatant of the solution obtained by the addition and stirring step. The emission wavelength of such carbon nanoparticle phosphors does not depend on the wavelength of the excitation light, making it possible to selectively obtain a desired emission wavelength. However, adjusting (tuning) the chromaticity has been difficult.

[0003] Graphene quantum dot phosphors have also been reported (see, for example, Non-Patent Document 1). Non-Patent Document 1 reports that nitrogen-doped graphene quantum dot phosphors are produced by hydrothermal synthesis using citric acid and ethylenediamine, and that the emission wavelength changes as the wavelength of incident light changes. However, chromaticity cannot be adjusted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 163955 [Non-patent literature]

[0005] [Non-Patent Document 1] Dan Qu et al., SCIENTIFIC REPORTS 4,5294,2014 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a method for producing a carbon nanoparticle phosphor with tuned chromaticity, a carbon nanoparticle phosphor with tuned chromaticity obtained thereby, a light-emitting device using the same, and a test paper using the same. [Means for solving the problem]

[0007] The method for producing a carbon nanoparticle phosphor with adjusted chromaticity according to the present invention includes preparing a raw material solution in which at least a carbon source is dissolved in an organic solvent, and heating the raw material solution, thereby solving the above-mentioned problems. The carbon source may be at least one selected from the group consisting of citric acid, citric acid monohydrate, ammonium citrate, benzoic acid, ascorbic acid, glucose, fructose, and sucrose. when the carbon nanoparticle phosphor is irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color of the emitted light satisfies 0.2≦x<0.3 and 0.25≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the organic solvent is a nitrogen-containing organic solvent; When irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies 0.3≦x<0.44 and 0.3≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the organic solvent is formamide and / or N-methylformamide, and the preparing step further comprises dissolving in the organic solvent at least one nitrogen source selected from the group consisting of ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), and cysteamine; When irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.44≦x≦0.6 and 0.3≦y≦0.45, the organic solvent is formamide, and the preparing step may further include dissolving at least one nitrogen source selected from the group consisting of ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine in the organic solvent. when irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies 0.2≦x<0.3 and 0.25≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the concentration of the carbon source in the organic solvent satisfies the range of 0.05 mol / L to 0.2 mol / L, when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor satisfies 0.3≦x<0.44 and 0.3≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the concentration of the carbon source in the organic solvent satisfies the range of 0.05 mol / L or more and 0.2 mol / L or less, and the concentration of the nitrogen source in the organic solvent satisfies the range of 0.05 mol / L or more and 1.5 mol / L or less; When irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies 0.44≦x≦0.6 and 0.3≦y≦0.45 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the concentration of the carbon source in the organic solvent may satisfy the range of 0.05 mol / L to 0.2 mol / L, and the concentration of the nitrogen source in the organic solvent may satisfy the range of 0.05 mol / L to 3.0 mol / L. when the carbon nanoparticle phosphor is irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color of the emitted light satisfies 0.2≦x<0.3 and 0.25≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the organic solvent is formamide; when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor satisfies 0.3≦x<0.44 and 0.3≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates, the organic solvent is formamide, the nitrogen source is at least one selected from the group consisting of ethylenediamine, diethanolamine, and urea, When irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.44≦x≦0.6 and 0.3≦y≦0.45, the organic solvent may be formamide and the nitrogen source may be ammonium hydroxide. The carbon source may be citric acid. Heating the raw material solution may involve heating the raw material solution at a temperature of 150° C. or higher and 230° C. or lower for a period of 5 hours or higher and 15 hours or lower. The method may further include recovering a product produced by heating the raw material solution and heating the product in a vacuum. The heating in a vacuum may be performed by heating the product at a temperature of 50°C to 70°C under a vacuum of 1 Pa to 10,000 Pa. temperature The mixture may be heated for a period of at least 30 minutes and not more than 12 hours. The carbon nanoparticle phosphor containing carbon, oxygen, nitrogen, and hydrogen elements according to the present invention contains amorphous carbon and graphite-like carbon, and the nitrogen element includes pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen, thereby solving the above-mentioned problems. The content of the pyridine-type nitrogen may be greater than that of the graphite-type nitrogen, the amorphous carbon may be in the range of more than 90 volume % to 99 volume % or less, the graphite-like carbon may be in the range of 1 volume % to less than 10 volume %, and when irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor may satisfy the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.2≦x<0.3 and 0.25≦y≦0.4. The amorphous carbon may be present in an amount of 95% by volume or more and 99% by volume or less, and the graphite carbon may be present in an amount of 1% by volume or more and 5% by volume or less. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are respectively expressed as follows: 0.58≦p≦0.65 0.22≦q≦0.30 0.12≦r<0.16 may be satisfied. The carbon element and nitrogen element contents p and q are 0.38 may be satisfied. The content of the pyridine-type nitrogen may be less than that of the graphite-type nitrogen, the amorphous carbon may be in the range of 45% by volume or more and 70% by volume or less, and the graphite-like carbon may be in the range of 30% by volume or more and 55% by volume or less. When irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor may satisfy the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.3≦x<0.44 and 0.3≦y≦0.4. ​The amorphous carbon may be present in an amount ranging from 53% to 68% by volume, and the graphite carbon may be present in an amount ranging from 32% to 47% by volume. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are respectively expressed as follows: 0.57≦p≦0.65 0.20≦q<0.26 0.16≦r<0.19 may be satisfied. The carbon element and nitrogen element contents p and q are 0.32 may be satisfied. The content of the pyridine-type nitrogen may be less than that of the graphite-type nitrogen, the amorphous carbon may be in the range of 60% by volume or more and 90% by volume or less, the graphite-like carbon may be in the range of 10% by volume or more and 40% by volume or less, and when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor may satisfy the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.44≦x≦0.6 and 0.3≦y≦0.45. The amorphous carbon may be present in an amount of 60% by volume or more and 83% by volume or less, and the graphite carbon may be present in an amount of 17% by volume or more and 40% by volume or less. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are respectively expressed as follows: 0.58≦p≦0.65 0.15≦q≦0.21 0.19≦r≦0.21 may be satisfied. The carbon element and nitrogen element contents p and q are 0.25 may be satisfied. ​​The carbon nanoparticle phosphor may have a diameter in the range of 1 nm to 20 nm. A light emitting device according to the present invention comprises at least an excitation source and a phosphor, and the phosphor comprises the above-mentioned carbon nanoparticle phosphor, thereby solving the above-mentioned problems. The phosphor may be a resin molded body in which the carbon nanoparticle phosphor is dispersed. The test paper according to the present invention for determining whether a test liquid contains water contains the above-mentioned carbon nanoparticle fluorescent material, thereby solving the above-mentioned problems. [Effects of the Invention]

[0008] The method for producing a carbon nanoparticle phosphor with chromaticity adjustment of the present invention includes preparing a raw material solution by dissolving at least a carbon source in an organic solvent and heating the raw material solution. The chromaticity can be adjusted (tuned) by appropriately selecting the type and concentration of the carbon source, the type of organic solvent, and the type and concentration of the nitrogen source. The carbon nanoparticle phosphor of the present invention contains carbon, oxygen, nitrogen, and hydrogen, and also contains amorphous carbon and graphite-like carbon, where the nitrogen element includes pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen. The above-described method allows for the adjustment of the ratio of amorphous carbon to graphite-like carbon, thereby controlling the composition ratio, thereby adjusting the chromaticity. Using such a phosphor, a light-emitting device can be provided that has a chromaticity near the blackbody locus and emits light relatively close to natural light. The phosphor of the present invention exhibits reduced luminescence intensity in response to water, allowing for the provision of a test paper for determining whether a liquid contains water based on changes in luminescence intensity. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a flow for producing a carbon nanoparticle phosphor with adjusted chromaticity according to the present invention. [Figure 2] Schematic diagram showing a light-emitting device using the carbon nanoparticle phosphor of the present invention. [Figure 3] Schematic diagram showing a test paper using the carbon nanoparticle phosphor of the present invention. [Figure 4]FIG. 1 shows the reaction formula of Example 1 and the luminescence of the liquid sample of Example 1. [Figure 5] FIG. 1 shows reaction formulas for Examples 2 to 6 and luminescence states of liquid samples for Examples 2 to 6. [Figure 6] 1 shows reaction formulas of Examples 7 and 8 and luminescence patterns of liquid samples of Examples 7 and 8. [Figure 7] FIG. 1 shows XRD patterns of powder samples of Examples 1, 2, and 7. [Figure 8] TEM images of the liquid sample of Example 1 at various magnifications. [Figure 9] TEM images of the liquid sample of Example 2 at various magnifications. [Figure 10] TEM images of the liquid sample of Example 7 at various magnifications. [Figure 11] FIG. 1 shows XPS spectra of liquid samples of Examples 1, 2, and 7. [Figure 12] Figure 1 shows the deconvoluted HRXPS spectrum of the liquid sample in Example 1. [Figure 13] Figure 1 shows the deconvoluted HRXPS spectrum of the liquid sample in Example 2. [Figure 14] Figure 1 shows the deconvoluted HRXPS spectrum of the liquid sample of Example 7. [Figure 15] FIG. 15 is a diagram showing the change in the amount of nitrogen doping centers calculated from FIGS. 12 to 14. [Figure 16] FIG. 1 shows ATR-FTIR spectra of liquid samples of Examples 1, 2, and 7. [Figure 17] FIG. 1 shows the absorption spectra of the liquid samples of Examples 1, 2, and 7. [Figure 18] FIG. 1 shows the emission spectra of the liquid samples of Examples 1, 2, and 7. [Figure 19] FIG. 1 shows the absorption spectra of liquid samples from Examples 3 and 4. [Figure 20] FIG. 1 shows the absorption spectra of liquid samples in Examples 5 and 6. [Figure 21] CIE chromaticity diagram plotting the emission of liquid samples from Examples 1 to 8 [Figure 22] Figure showing two-dimensional emission mapping of the liquid sample in Example 1 [Figure 23]Figure showing two-dimensional emission mapping of the liquid sample in Example 2 [Figure 24] Figure 10 shows two-dimensional emission mapping of the liquid sample of Example 7. [Figure 25] FIG. 10 shows the appearance of a resin molded body according to Example 9. [Figure 26] FIG. 10 is a diagram showing the fluorescence spectrum of the resin molded body according to Example 9. [Figure 27] CIE chromaticity diagram plotting the luminescence of the resin molding according to Example 9 [Figure 28] Diagram showing the manufacturing procedure and testing of test strips [Figure 29] A diagram showing the process of determination using test paper [Figure 30] Emission spectra for various types of water [Figure 31] 30 shows the dependence of the luminescence intensity on the concentration of heavy water DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are designated by like numbers and their description will be omitted.

[0011] (Embodiment 1) In the first embodiment, a method for producing a carbon nanoparticle phosphor of the present invention in which the chromaticity is adjusted (tuned), and the carbon nanoparticle phosphor obtained thereby will be described.

[0012] FIG. 1 is a diagram showing a flow chart for producing a carbon nanoparticle phosphor with adjusted chromaticity according to the present invention.

[0013] Step S110: A raw material solution is prepared by dissolving at least a carbon source in an organic solvent. Step S120: Heating the raw material solution. The inventors of the present invention have discovered that carbon nanoparticle phosphors can be obtained simply by heating a carbon source using an organic solvent, rather than by hydrothermal synthesis, and have found through experiments that the chromaticity can be adjusted along the blackbody locus by appropriately selecting the type and concentration of the carbon source, the type and concentration of the organic solvent, and the type and concentration of the nitrogen source. Each step will be described in detail.

[0014] The carbon source used in step S110 is not particularly limited as long as it is an organic substance that is decomposed by heating in step S120 to produce carbon, but is preferably at least one selected from the group consisting of citric acid, citric acid monohydrate, ammonium citrate, benzoic acid, ascorbic acid, glucose, fructose, and sucrose. These organic substances are easily available and can be decomposed by heating in step S120 to form a carbon nanoparticle phosphor. Among these, citric acid is preferred because it can produce a carbon nanoparticle phosphor that achieves a chromaticity and color temperature on or near the blackbody locus.

[0015] The organic solvent used in step S110 is not particularly limited, but preferably contains nitrogen. By including nitrogen, nitrogen-doped carbon nanoparticle phosphors can be obtained. Such organic solvents include formamide and / or N-methylformamide. These are preferred because they can dissolve the carbon source described above.

[0016] In step S110, a raw material solution may be prepared by dissolving a nitrogen source in an organic solvent in addition to the carbon source described above. This allows for control of the amount of nitrogen doping. Examples of such nitrogen sources include ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), cysteamine, ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine. These can be dissolved in organic solvents and allow for doping with pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, graphite-type nitrogen, and the like.

[0017] Step S120 produces amorphous carbon and graphitic carbon. The heating conditions are not particularly limited as long as they decompose the carbon source and allow the carbon to react with the nitrogen in the organic solvent or the nitrogen in the nitrogen source. Preferably, the raw material solution is heated at a temperature of 150°C to 230°C for 5 to 15 hours. Under these conditions, the reaction proceeds efficiently, resulting in the production of carbon nanoparticle phosphors. More preferably, heating is performed at a temperature of 170°C to 210°C for 7 to 10 hours.

[0018] In this way, the carbon nanoparticle phosphor is obtained in a dispersed state in the solvent. However, if the carbon nanoparticle phosphor is to be obtained in powder form, the obtained product may be recovered by centrifugation or the like and heated in a vacuum, as shown in step S130 of FIG. 1.

[0019] Preferably, the product is heated at a temperature of 50°C to 70°C under a vacuum of 1 Pa to 10,000 Pa. temperature The mixture is heated for 30 minutes to 12 hours, which allows the product to be efficiently recovered.

[0020] The present inventors have found that by selecting a carbon source, an organic solvent, and, if necessary, a nitrogen source, and adjusting their concentrations, it is possible to provide carbon nanoparticle phosphors whose chromaticity is adjusted and which lie on or near the blackbody locus. For ease of understanding, carbon nanoparticle phosphors whose chromaticity is adjusted in this manner will be referred to as cyan, white, or orange carbon nanoparticle phosphors, and methods for producing these phosphors will be described.

[0021] <Cyan> A cyan carbon nanoparticle phosphor is a carbon nanoparticle phosphor that, when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, emits light whose color satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.2≦x<0.3 and 0.25≦y≦0.4.

[0022] In this case, in step S110, it is sufficient to prepare a raw material solution by dissolving the above-mentioned carbon source in a nitrogen-containing organic solvent. This results in a solution with a higher content of pyridine-type nitrogen than that of graphite-type nitrogen, containing amorphous carbon in the range of more than 90% by volume to 99% by volume and graphite-like carbon in the range of 1% by volume to 10% by volume, thereby achieving the above-mentioned emission color. Here, the total amount of amorphous carbon and graphite-like carbon is 100% by volume.

[0023] More preferably, the concentration of the carbon source in the organic solvent is in the range of 0.05 mol / L to 0.2 mol / L, which allows for the production of a cyanide-based carbon nanoparticle phosphor containing amorphous carbon in an amount of 95 vol % to 99 vol % and graphitic carbon in an amount of 1 vol % to 5 vol %.

[0024] Preferably, the concentration of the carbon source in the organic solvent is in the range of 0.1 mol / L or more and 0.15 mol / L or less. More preferably, the organic solvent is formamide, and the carbon source is citric acid. In this case, the predetermined composition formula described below is satisfied, and the deviation (Duv) from the blackbody locus within the chromaticity coordinates can be suppressed to within ±0.03. The deviation from the blackbody locus was evaluated in accordance with the evaluation method disclosed in JIS Z8725.

[0025] <White type> A white carbon nanoparticle phosphor is a carbon nanoparticle phosphor whose emitted color when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.3≦x<0.44 and 0.3≦y≦0.4.

[0026] In this case, in step S110, the carbon source is dissolved in formamide and / or N-methylformamide as an organic solvent, and at least one nitrogen source selected from the group consisting of ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), and cysteamine is further dissolved to prepare a raw material solution. This results in a white carbon nanoparticle phosphor containing less pyridine-type nitrogen than graphite-type nitrogen and containing 45% to 70% by volume of amorphous carbon and 30% to 55% by volume of graphite-like carbon. Here, the total amount of amorphous carbon and graphite-like carbon is 100% by volume.

[0027] More preferably, the concentration of the carbon source in the organic solvent is in the range of 0.05 mol / L to 0.2 mol / L, and the concentration of the nitrogen source in the organic solvent is in the range of 0.05 mol / L to 1.5 mol / L. Within these ranges, a white carbon nanoparticle phosphor containing amorphous carbon in the range of 53 vol% to 68 vol% and graphitic carbon in the range of 32 vol% to 47 vol% can be obtained.

[0028] Preferably, the concentration of the carbon source in the organic solvent is in the range of 0.1 mol / L to 0.15 mol / L, and the concentration of the nitrogen source in the organic solvent is in the range of 0.05 mol / L to 1.0 mol / L, which allows efficient production of a white carbon nanoparticle phosphor.

[0029] More preferably, the organic solvent is formamide, the carbon source is citric acid, and the nitrogen source is at least one selected from the group consisting of ethylenediamine, diethanolamine, and urea. In this case, the specified composition formula described below is satisfied, and the deviation from the blackbody locus in the chromaticity coordinates can be suppressed to within ±0.01.

[0030] <Orange> An orange carbon nanoparticle phosphor is a carbon nanoparticle phosphor that, when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, emits light whose color satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.44≦x≦0.6 and 0.3≦y≦0.45.

[0031] In this case, in step S110, the carbon source is dissolved in formamide as an organic solvent, and at least one nitrogen source selected from the group consisting of ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine is further dissolved to prepare a raw material solution. This results in a content of pyridine-type nitrogen lower than that of graphite-type nitrogen, and an orange carbon nanoparticle phosphor containing amorphous carbon in a range of 60% to 90% by volume and graphite-like carbon in a range of 10% to 40% by volume. Here, the total amount of amorphous carbon and graphite-like carbon is 100% by volume.

[0032] More preferably, the concentration of the carbon source in the organic solvent is in the range of 0.05 mol / L to 0.2 mol / L, and the concentration of the nitrogen source in the organic solvent is in the range of 0.05 mol / L to 3.0 mol / L. Within these ranges, an orange carbon nanoparticle phosphor can be obtained that contains amorphous carbon in an amount of 77 vol % to 83 vol % and graphitic carbon in an amount of 17 vol % to 23 vol %.

[0033] More preferably, the concentration of the carbon source in the organic solvent is in the range of 0.1 mol / L to 0.15 mol / L, and the concentration of the nitrogen source in the organic solvent is in the range of 0.5 mol / L to 2.5 mol / L. Within these ranges, an orange carbon nanoparticle phosphor can be efficiently obtained. Even more preferably, the concentration of the nitrogen source in the organic solvent is in the range of 0.5 mol / L to 1 mol / L.

[0034] More preferably, the organic solvent is formamide, the carbon source is citric acid, and the nitrogen source is ammonium hydroxide. In this case, the specified composition formula described below is satisfied, and the deviation from the blackbody locus in the chromaticity coordinates can be suppressed to within ±0.01.

[0035] Next, the carbon nanoparticle phosphor of the present invention obtained in this manner will be described. The nanoparticle phosphor of the present invention is primarily composed of carbon, but by using the above-mentioned raw material solution, it contains carbon, oxygen, nitrogen, and hydrogen. The primary carbon component contains amorphous carbon and graphite-like carbon, and controlling the amounts of these components allows for control of the emission color, chromaticity, and color temperature. Amorphous carbon is non-crystalline carbon, while graphite-like carbon is crystalline carbon. In powder X-ray diffraction, if a broad peak is observed near 2θ = 20.5°, it is determined that amorphous carbon is present, and if a sharp peak is observed near 2θ = 27°, it is determined that graphite-like carbon is present.

[0036] The nanoparticle phosphor of the present invention contains pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen as nitrogen elements. The emission color, chromaticity, and color temperature can be controlled by adjusting the content of these elements. Here, pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen are represented by the following structural formula. Note that R in the amide-type nitrogen may be hydrogen or an alkyl group having 1 to 5 carbon atoms. The presence of these nitrogen elements can be determined from the peak position of the N1s spectrum obtained by X-ray photoelectron spectroscopy (XPS) measurement. These nitrogen elements are sometimes collectively referred to as nitrogen doping centers.

[0037] [ka]

[0038] The inventors of the present application have discovered that carbon nanoparticle phosphors can be obtained by the above-mentioned production method, and that by controlling the amounts of amorphous carbon and graphite carbon, the quantitative relationship between the nitrogen doping centers, and the composition, in particular, carbon nanoparticle phosphors with adjusted chromaticity and even on or near the blackbody locus can be obtained. For ease of understanding, these carbon nanoparticle phosphors with adjusted chromaticity will be referred to as cyan, white, and orange carbon nanoparticle phosphors and these phosphors will be described.

[0039] <Cyan> A cyan carbon nanoparticle phosphor is a carbon nanoparticle phosphor that, when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, emits light whose color satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.2≦x<0.3 and 0.25≦y≦0.4.

[0040] In this case, the content of pyridine-type nitrogen is greater than that of graphite-type nitrogen. Furthermore, if the total amount of amorphous carbon and graphite-like carbon is taken as 100 volume %, the cyan carbon nanoparticle phosphor contains amorphous carbon in a range of more than 90 volume % to 99 volume % and graphite-like carbon in a range of 1 volume % to less than 10 volume %. The significant increase in amorphous carbon results in cyan emission. The content of amorphous carbon and graphite-like carbon is calculated from the intensity ratio of the peaks at 2θ = 20.5° and 27° in powder X-ray diffraction.

[0041] The cyan carbon nanoparticle phosphor more preferably contains 95% by volume or more and 99% by volume or less of amorphous carbon and 1% by volume or more and 5% by volume or less of graphite carbon, which can result in a phosphor with good color purity.

[0042] In the cyan carbon nanoparticle phosphor, preferably, the carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are each 0.58≦p≦0.65 0.22≦q≦0.30 0.12≦r<0.16 This makes it possible to suppress the deviation from the blackbody locus in the chromaticity coordinates to within the range of ±0.03. More preferably, the contents p and q are 0.38 or less.

[0043] <White type> A white carbon nanoparticle phosphor is a carbon nanoparticle phosphor whose emitted color when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.3≦x<0.44 and 0.3≦y≦0.4.

[0044] In this case, the content of pyridine-type nitrogen is less than that of graphite-type nitrogen, and the white carbon nanoparticle phosphor contains amorphous carbon in a range of 45% to 70% by volume and graphite-like carbon in a range of 30% to 55% by volume. The amorphous carbon content is greater than that of graphite-like carbon. Here, the total amount of amorphous carbon and graphite-like carbon is taken as 100% by volume.

[0045] The white carbon nanoparticle phosphor more preferably contains 53 to 68 volume % of amorphous carbon and 32 to 47 volume % of graphite carbon, which enables blue-white, white, and warm-white emission.

[0046] In the white carbon nanoparticle phosphor, preferably, the carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are each 0.57≦p≦0.65 0.20≦q<0.26 0.16≦r<0.19 ​This makes it possible to suppress the deviation from the blackbody locus in the chromaticity coordinates to within the range of ±0.01. More preferably, the contents p and q are 0.32 or less.

[0047] <Orange> An orange carbon nanoparticle phosphor is a carbon nanoparticle phosphor that, when irradiated with light having a wavelength in the range of 300 nm or more and 380 nm or less, emits light whose color satisfies the (x, y) values ​​on the CIE 1931 chromaticity coordinates of 0.44≦x≦0.6 and 0.3≦y≦0.45.

[0048] In this case, the content of pyridine-type nitrogen is less than that of graphite-type nitrogen. The orange carbon nanoparticle phosphor contains amorphous carbon in a range of 60% to 90% by volume and graphite-like carbon in a range of 10% to 40% by volume. Here, the total amount of amorphous carbon and graphite-like carbon is 100% by volume.

[0049] The orange carbon nanoparticle phosphor more preferably contains amorphous carbon in a range of 60% by volume to 83% by volume and graphite carbon in a range of 17% by volume to 40% by volume, thereby enabling emission of light with good color purity.

[0050] In the orange carbon nanoparticle phosphor, preferably, the carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are each 0.58≦p≦0.65 0.15≦q≦0.21 0.19≦r≦0.21 This makes it possible to suppress the deviation from the blackbody locus in the chromaticity coordinates to within the range of ±0.01. More preferably, the contents p and q are 0.25 or less.

[0051] ​​As described above, the carbon nanoparticle phosphor of the present invention emits light with chromaticity adjusted by controlling the amount of amorphous carbon and graphitic carbon, the amount of nitrogen doping center, and the composition. What is particularly noteworthy is that a single material can emit light with a deviation of ±0.01 from the blackbody locus.

[0052] In addition, the carbon nanoparticle phosphor of the present invention emits light when irradiated with light (excitation light) having a wavelength in the range of 300 nm to 380 nm, but the emission wavelength also changes as the wavelength of the excitation light changes. That is, as the wavelength of the excitation light becomes longer, the emission wavelength also red-shifts to the longer wavelength side. For example, when a white carbon nanoparticle phosphor is irradiated with light having a wavelength in the range of 300 nm to 380 nm, the (x, y) values ​​on the CIE 1931 chromaticity coordinate satisfy 0.3≦x<0.44 and 0.3≦y≦0.4, and it emits white light. However, when the excitation light has a wavelength of 450 nm, it emits green light, when the excitation light has a wavelength of 525 nm, it emits yellow-green light, when the excitation light has a wavelength of 550 nm, it emits orange light, and when the excitation light has a wavelength of 600 nm, it emits red light.

[0053] The carbon nanoparticle phosphor of the present invention is made of nanoparticles having a particle size on the nano-order, preferably having a diameter in the range of 1 nm to 20 nm, which provides high luminous efficiency.

[0054] The carbon nanoparticle phosphor of the present invention may have functional groups or bonds such as -OH, -CONH2, C=O, -COOH, C=C, OC=O, CH, and NH. This allows for highly efficient visible light emission. These bonds are confirmed by infrared absorption spectroscopy.

[0055] The carbon nanoparticle phosphor of the present invention may be dispersed in a solvent, resin, or the like. This reduces the effect of concentration quenching and increases luminous efficiency. Such solvents may include, for example, dimethyl sulfoxide (DMSO), dimethylformamide, or water, in addition to the organic solvents used in the synthesis. The resin may be any water-soluble polymer that transmits light having wavelengths from the ultraviolet to the visible range, such as polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyethyleneimine, polyethylene oxide, polyvinylpyrrolidone, or carboxyl vinyl polymer. Such resins can be used to provide resin molded products, such as thin films formed by spin coating or dripping, bulk products formed by drying, and fibers formed by electrospinning. Such resin molded products are easy to handle.

[0056] When dispersed in a solvent, resin, or the like, the carbon nanoparticle phosphor content is preferably in the range of 0.01% by mass to 5% by mass. Within this range, high luminescence intensity and high quantum efficiency can be expected. More preferably, the carbon nanoparticle phosphor content is in the range of 0.01% by mass to 1% by mass.

[0057] (Embodiment 2) In the second embodiment, a light emitting device using the carbon nanoparticle phosphor of the present invention will be described. FIG. 2 is a schematic diagram showing a light-emitting device using the carbon nanoparticle phosphor of the present invention.

[0058] The light emitting device of the present invention includes at least an excitation source and a phosphor, and the phosphor includes the carbon nanoparticle phosphor described above. With this configuration, a light emitting device having a desired emission color can be provided.

[0059] The excitation source may be a light-emitting diode, a laser diode, an organic electroluminescence (EL), a semiconductor laser, a fluorescent lamp, etc., and those that emit light having a peak in the range of 200 nm to 600 nm are used. Among them, a purple light-emitting diode having a peak in the range of 330 nm to 420 nm is preferred because it can efficiently excite the carbon nanoparticle phosphor of the present invention.

[0060] Light-emitting device 200 in Fig. 2 is a substrate-mounted white light-emitting diode lamp. Light-emitting device 200 has lead wires 210 and 220, which are fixed to white alumina substrate 230, which has high visible light reflectance. A purple light-emitting diode element 240 with an emission peak wavelength of 405 nm is placed on one end of one lead wire 210 and electrically connected to it using a conductive paste or the like. Purple light-emitting diode element 240 is electrically connected to the other lead wire 220 by a thin gold wire 250. The other ends of lead wires 210 and 220 extend outside and function as electrodes.

[0061] Purple light-emitting diode element 240 is covered with resin molded body 260 in which the carbon nanoparticle phosphor of the present invention is dispersed in resin. Here, the carbon nanoparticle phosphor is a white carbon nanoparticle phosphor. Wall member 280 made of white silicone resin or the like is provided on alumina substrate 230, and purple light-emitting diode element 240 covered with resin molded body 260 is located in the center of wall member 280. Purple light-emitting diode element 240 covered with resin molded body 260 is sealed in the center of wall member 280 with transparent resin 270 such as epoxy resin.

[0062] When current is applied to lead wires 210, 220 of light-emitting device 200, purple light-emitting diode element 240 emits light with a peak wavelength of 405 nm. This light enters resin molded body 260 of the present invention, exciting the carbon nanoparticle phosphors in resin molded body 260, which then emit white light. The white light passes through resin 270 and exits to the outside. In this way, light-emitting device 200 functions to emit white light.

[0063] Here, resin molding 260 is configured to cover purple light-emitting diode element 240, but is not limited to this. For example, resin molding 260 may be placed on the light-emitting surface of purple light-emitting diode element 240, or may be placed on resin 270. Alternatively, instead of resin 270, the entire body may be resin molding 260.

[0064] Although the resin molded body 260 has been described as containing only a carbon nanoparticle phosphor that emits white light, it goes without saying that a cyan carbon nanoparticle phosphor or an orange carbon nanoparticle phosphor may also be used. Furthermore, a wavelength-tunable laser may be used instead of the purple light-emitting diode element to provide a light-emitting device that can be tuned from white to red. Such modifications are also within the scope of the present invention.

[0065] Although a substrate-mounted white light-emitting diode lamp has been described with reference to Fig. 2, the carbon nanoparticle phosphor of the present invention may also be used in a bullet-type white light-emitting diode lamp. Such modifications can be easily made by those skilled in the art.

[0066] (Embodiment 3) In the third embodiment, a test paper using the carbon nanoparticle phosphor of the present invention will be described. The inventors of the present invention have discovered that the luminescence intensity of the carbon nanoparticle phosphor of the present invention decreases when it comes into contact with water (HO) or heavy water (DO). By utilizing this property, a test paper can be provided that can easily determine whether a test solution contains water (HO) or heavy water (DO).

[0067] FIG. 3 is a schematic diagram showing a test paper using the carbon nanoparticle phosphor of the present invention.

[0068] The test paper 300 comprises a mount 320 with an inspection area 310. The inspection area 310 contains the carbon nanoparticle phosphor described in the first embodiment. The mount 320 can be made of any paper capable of supporting the dispersed carbon nanoparticle phosphor, but is preferably made of cellulose fiber. Cellulose fiber has surface functional groups such as -OH and -COOH, which adsorb the carbon nanoparticle phosphor and prevent it from aggregating with other particles. Therefore, the use of cellulose fiber can provide a test paper that suppresses concentration quenching, has excellent luminescence intensity, and allows easy visual evaluation.

[0069] Although six test areas 310 are shown in Figure 3, the test area may cover the entire mount. This division is advantageous for simultaneously identifying multiple test liquids. Such a test paper 300 is manufactured by dropping a composition in which carbon nanoparticle fluorescent material is dispersed onto a mount 320 and then drying it.

[0070] Next, a method for determining whether a test liquid contains water using such a test paper 300 will be described. Here, the water may be light water (H2O) or heavy water (D2O). First, a liquid containing no water is dropped as a control into one of the test areas 310 of the test paper 300. Next, the test liquid is dropped into the other areas, and an excitation source is irradiated to observe the light emission. If there is a test area where the light emission intensity is visually lower than that of the control, it can be determined that the test liquid in that area contains water.

[0071] Since the emission intensity decreases linearly with the water content, if the relationship between the water content and the emission intensity is previously determined, the water content can be determined by measuring the emission spectrum.

[0072] Furthermore, the luminescence intensity of the carbon nanoparticle phosphor of the present invention differs depending on whether the carbon nanoparticle phosphor contains light water or heavy water. The higher the ratio of heavy water, the higher the luminescence intensity, and the higher the ratio of light water, the lower the luminescence intensity. By utilizing these characteristics, the content of light water or heavy water in a test solution can be determined.

[0073] The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples. [Example]

[0074] [Example 1 to Example 8] In Examples 1 to 8, carbon nanoparticle phosphors were synthesized using a solvothermal method.

[0075] Specifically, a raw material solution was prepared by dissolving citric acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as a carbon source, and optionally ethylenediamine (EDA, manufactured by Sigma-Aldrich Corporation, purity >99.5%, specific gravity D = 0.899 g / mL) as nitrogen sources, dimethylamine (DEA, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), urea (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and ammonium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) in formamide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as an organic solvent under the conditions shown in Table 1 (step S110 in FIG. 1). Next, the raw material solution was heated under the heating conditions shown in Table 1 (step S120 in FIG. 1).

[0076] The resulting product was centrifuged (rotation speed: 800 rpm) and washed several times with Milli-Q water and ethanol. The washed product was dried in vacuum (vacuum degree: 1 to 1000 Pa) at 60°C for 4 hours. In this way, powder samples of Examples 1 to 8 were obtained. Next, the powder samples of Examples 1 to 8 were dispersed in dimethyl sulfoxide (DMSO, Fujifilm Wako Pure Chemical Industries, Ltd.) and passed through a 20 nm syringe. At this time, the concentration of the product in DMSO was 0.0025 mass% (0.025 mg / mL). In this way, liquid samples of Examples 1 to 8 were obtained.

[0077] [Table 1]

[0078] The liquid samples of Examples 1 to 8 were irradiated with a lamp emitting light with a wavelength of 365 nm. The results are shown in Figures 4 to 6. The powder samples of Examples 1 to 8 were subjected to X-ray diffraction analysis using an X-ray diffractometer (Rigaku, Rint Ultima III). The results are shown in Figure 7. The liquid samples of Examples 1 to 8 were prepared by the dispersion method and observed using a high-resolution transmission electron microscope (HR-TEM) (JEOL, JEM 2100F). The results are shown in Figures 8 to 10. The chemical state and composition of the liquid samples of Examples 1 to 8 were analyzed using an X-ray photoelectron spectroscopy (XPS) analyzer (ULVAC-PHI, Quautera SXM). The results are shown in Figures 11 to 15 and Table 2.

[0079] The FTIR spectra of the liquid samples of Examples 1 to 8 were obtained by attenuated total reflection infrared spectroscopy (ATR-FTIR) using a spectrophotometer (Nicolet iS50 FTIR, manufactured by Thermo Scientific). Each measurement was accumulated 50 times. The results are shown in Figure 16. The absorption spectra of the liquid samples of Examples 1 to 8 were measured using an ultraviolet-visible-near-infrared spectrophotometer (V-570, manufactured by JASCO Corporation). The results are shown in Figure 17. The emission spectra of the liquid samples of Examples 1 to 8 were measured using a spectrofluorometer (FP-8500, manufactured by JASCO Corporation). The CIE chromaticity (x, y) was calculated from the emission spectra. These results are shown in Figures 18 to 24. These results will be summarized below.

[0080] FIG. 4 is a diagram showing the reaction formula of Example 1 and the luminescence of the liquid sample of Example 1. FIG. 5 shows the reaction formulas of Examples 2 to 6 and the luminescence states of the liquid samples of Examples 2 to 6. In FIG. FIG. 6 shows the reaction formulas of Examples 7 and 8 and the luminescence of the liquid samples of Examples 7 and 8. In FIG.

[0081] 4 to 6 are shown in gray scale, and FIG. 4 shows that when the liquid sample of Example 1 was irradiated with an ultraviolet lamp, it emitted blue (cyan-based) light. FIG. 5 shows that when the liquid samples of Examples 2 to 6 were irradiated with an ultraviolet lamp, they emitted light in a range of colors from bluish-white to white to warm white (white-based). FIG. 6 shows that when the liquid samples of Examples 7 and 8 were irradiated with an ultraviolet lamp, they emitted light in an orange (orange-based) color. This demonstrates that a fluorescent composition (phosphor) can be obtained by carrying out the method described in FIG. 1. Furthermore, as shown in Table 1, it was demonstrated that the emitted color can be changed by selecting the nitrogen source and concentration.

[0082] FIG. 7 shows XRD patterns of the powder samples of Examples 1, 2 and 7.

[0083] As shown in Figure 7, all XRD patterns show a broad peak near 2θ = 20.5° and a sharp peak near 2θ = 27°, indicating that amorphous carbon and graphite-like carbon are the main components. Although not shown, the powder samples of Examples 3 to 6 and 8 also showed similar patterns. The volume percentages of amorphous carbon and graphite-like carbon were calculated from the peak intensity ratios. The results are shown in Table 2.

[0084] [Table 2]

[0085] Table 2 shows that the amorphous carbon content is higher than that of graphite-like carbon, but the content varies depending on the emission color. Phosphors that emit cyan light have very little graphite-like carbon and significantly more amorphous carbon, phosphors that emit white light have a relatively large amount of graphite-like carbon but more amorphous carbon, and phosphors that emit orange light have a small amount of graphite-like carbon and more amorphous carbon.

[0086] FIG. 8 shows TEM images of the liquid sample of Example 1 at various magnifications. FIG. 9 shows TEM images of the liquid sample of Example 2 at various magnifications. FIG. 10 shows TEM images of the liquid sample of Example 7 at various magnifications.

[0087] In Figure 8, a layer structure derived from amorphous carbon was confirmed, as indicated by the dotted line. Furthermore, when the circled area was enlarged, lattice fringes were confirmed, indicating crystalline graphite-like carbon. In Figures 9 and 10, numerous nanoparticles, indicated by black spots, were confirmed, and their particle sizes were found to be in the range of 1 nm to 20 nm. The particle size was determined by obtaining a transmission electron microscope (TEM) image at a magnification of 1000x or more, measuring the particle sizes of at least 100 nanoparticles in any 500 nm square area, and averaging the results. Because nanoparticles are not perfectly spherical, the longest diameter was used to determine the particle size of the nanoparticle. These findings demonstrate that carbon nanoparticle phosphors were dispersed in the liquid sample.

[0088] FIG. 11 shows XPS spectra of the liquid samples of Examples 1, 2 and 7.

[0089] 11, it was found that carbon, oxygen, and nitrogen elements were present in the carbon nanoparticle phosphors in the liquid samples of Examples 1, 2, and 7. Note that peaks due to elements in the solvent (DMSO) have been removed from the XPS spectra. The liquid samples of Examples 3 to 6 and 8 also exhibited similar XPS spectra.

[0090] [Table 3]

[0091] According to the composition analysis in Table 3, in the carbon nanoparticle phosphor of the present invention, the carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are, respectively: 0.58≦p≦0.65 0.22≦q≦0.30 0.12≦r<0.16 If the above condition is satisfied, blue (cyan) light is emitted. 0.57≦p≦0.65 0.20≦q<0.26 0.16≦r<0.19 If the above conditions are met, the light will be bluish white to white to warm white (white-based), 0.58≦p≦0.65 0.15≦q≦0.21 0.19≦r≦0.21 It was shown that when the above condition is satisfied, orange light is emitted.

[0092] FIG. 12 shows the deconvoluted HRXPS spectrum of the liquid sample of Example 1. FIG. 13 shows the deconvoluted HRXPS spectrum of the liquid sample of Example 2. FIG. 14 shows the deconvoluted HRXPS spectrum of the liquid sample of Example 7.

[0093] 12 to 14 show the results of deconvolution of the N-1s peak in the XPS spectrum shown in FIG. 11. As shown in FIGS. 12 to 14, four main peaks were observed, corresponding to binding energies of 398.7 eV, 399.6 eV, 400.3 eV, and 401.3 eV, respectively. These peaks were determined to be types of nitrogen doping centers within the carbon framework, corresponding to pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen, respectively. Although not shown, the deconvoluted HRXPS spectra of the liquid samples of Examples 3 to 6 and 8 were similar.

[0094] FIG. 15 is a diagram showing the change in the amount of nitrogen doping center calculated from FIGS.

[0095] 15, it can be seen that the quantitative relationship of the nitrogen doping center differs depending on the emission color. In particular, the relationship between pyridine-type nitrogen and graphite-type nitrogen contributes to the emission color, and the same investigation was carried out for Examples 3 to 6 and 8. The results are shown in Table 4.

[0096] [Table 4]

[0097] According to Table 4, there is a tendency that the amount of pyridine-type nitrogen in phosphors that emit cyan light is greater than that in graphite-type nitrogen, the amount of pyridine-type nitrogen in phosphors that emit white light is less than that in graphite-type nitrogen, and the amount of pyridine-type nitrogen in phosphors that emit orange light is less than that in graphite-type nitrogen.

[0098] FIG. 16 shows ATR-FTIR spectra of the liquid samples of Examples 1, 2 and 7.

[0099] The carbon nanoparticle phosphors in the liquid samples of Examples 1, 2, and 7 were bonded by C=O bonds (1697 cm) via amide bonds. -1 around 1530cm), aromatic C=C bonds ( -1 around 1310-1380cm), OH and CH bonds due to phenol (1310-1380cm -1 This indicates that the carbon nanoparticle phosphor of the present invention has functional groups and bonds such as -OH, C=O, C=C, and CH.

[0100] FIG. 17 is a diagram showing the absorption spectra of the liquid samples of Examples 1, 2 and 7.

[0101] 17, it was found that all the samples well absorbed light in the wavelength range of 200 nm or more and 600 nm or less. Although not shown, the absorption spectra of the liquid samples of Examples 3 to 6 and Example 8 were also similar.

[0102] FIG. 18 shows the emission spectra of the liquid samples of Examples 1, 2 and 7. FIG. 19 is a diagram showing the absorption spectra of the liquid samples of Examples 3 and 4. FIG. 20 shows the absorption spectra of the liquid samples of Examples 5 and 6. As shown in FIG.

[0103] 18 to 20 show the emission spectra when each liquid sample was irradiated with light having an excitation wavelength of 370 nm. Figures 19 and 20 also show the emission spectrum of Example 2 shown in Figure 1.

[0104] The emission spectrum of Example 1 showed a peak at 450 nm, indicating blue light emission. The emission spectrum of Example 7 showed a peak at 616 nm, indicating orange light emission. On the other hand, the emission spectrum of Example 2, unlike those of Examples 1 and 7, showed a broad emission spectrum with multiple wavelength components, with peaks at 478 nm, 514 nm, and 612 nm. This also indicated that the carbon nanoparticle phosphor in the liquid sample of Example 2 emitted white light.

[0105] The emission spectra of Examples 3 to 6 showed broad emission spectra with multiple wavelength components, similar to that of Example 2, but it was shown that white light emission with different color rendering properties was produced due to differences in the intensities of each wavelength component.

[0106] From the above, by employing the method of the present invention, it is possible to provide carbon nanoparticle phosphors that emit blue (cyan-based), white, or orange light by selecting raw material components and adjusting their concentrations. Furthermore, the present invention can provide a method for synthesizing carbon nanoparticle phosphors that are excellent in adjusting color rendering properties.

[0107] FIG. 21 shows a CIE chromaticity diagram in which the luminescence of the liquid samples of Examples 1 to 8 is plotted.

[0108] The chromaticity x and y values ​​calculated from the emission spectra in Figures 18 to 20 were plotted on the CIE 1931 chromaticity diagram. Figure 21 also shows the blackbody locus. Carbon nanoparticle phosphors are available whose emission color can be changed by selecting raw materials and adjusting their concentrations, but surprisingly, it was found that the emission color can also change along the blackbody locus. For example, it was found that a white carbon nanoparticle phosphor that emits white light can emit light with a deviation of ±0.01 (a range of -0.01 to +0.01) from the blackbody locus, depending on the conditions.

[0109] FIG. 22 shows two-dimensional emission mapping of the liquid sample of Example 1. FIG. 23 shows two-dimensional emission mapping of the liquid sample of Example 2. FIG. 24 shows two-dimensional emission mapping of the liquid sample of Example 7.

[0110] 22 to 24 are shown in grayscale, with brighter areas indicating light emission. It was found from FIGS. 22 to 24 that for all liquid samples, the emission wavelength changes when the wavelength of the excitation light is changed. The dependency of the excitation wavelength on the emission wavelength for the liquid sample of Example 7 in FIG. 24 is smaller than that for the liquid samples of Example 1 in FIG. 22 and Example 2 in FIG. 23. This is thought to be because the liquid sample of Example 7 contains a carbon nanoparticle phosphor that emits orange light, but as shown in the absorption spectrum in FIG. 17, absorption decreases at wavelengths exceeding 600 nm, making it difficult to emit light. For simplicity, the above results are summarized in Table 5.

[0111] [Table 5]

[0112] [Example 9] In Example 9, the powder samples of Examples 2 to 4 were used to produce a thin film resin molded product in which carbon nanoparticle phosphors were dispersed in polyvinylpyrrolidone (PVP, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0113] PVP powder (2 g) was added to deionized water (60 mL) and kept at 90°C for 3 hours to prepare a PVP aqueous solution (PVP concentration: 3.3 mass%). The powder samples obtained in Examples 2 to 4 (100 μg each) were added to 4 mL of PVP aqueous solution and stirred. This was drop-cast onto a quartz substrate and dried at 90°C for 1 hour to obtain a thin-film resin molded product. The carbon nanoparticle phosphor content in the resin molded product thus obtained was 0.07 mass%. The powder samples in Examples 2 to 4 are referred to as W-CD1, W-CD2, and W-CD3, respectively, and the resulting resin molded products are referred to as W-CD1@PVP, W-CD2@PVP, and W-CD3@PVP.

[0114] The appearance of the resulting resin molded article was observed and irradiated with a lamp emitting light with a wavelength of 365 nm. The observation results are shown in Figure 25. The emission spectrum of the resin molded article was measured using a spectrofluorophotometer. The CIE chromaticity (x, y) was calculated from the emission spectrum. These results are shown in Figures 26 and 27. These results will be summarized below.

[0115] FIG. 25 is a diagram showing the appearance of the resin molded body according to Example 9. As shown in FIG.

[0116] 25(A) shows that the resin molded body of Example 9 is transparent in the visible region. 25(B) shows that when irradiated with an ultraviolet lamp, all of the resin molded bodies of Example 9 emit light in a range of bluish-white to white to warm white (white-based). These emission colors were similar to those of the liquid samples of Examples 2 to 4.

[0117] FIG. 26 is a diagram showing the fluorescence spectrum of the resin molded article of Example 9.

[0118] 26, all of the resin molded articles of Example 9 exhibited broad emission spectra, with multiple wavelength components having peaks at 478 nm, 514 nm, and 612 nm. Such emission spectra were similar to those of the liquid samples of Examples 2 to 4.

[0119] FIG. 27 shows a CIE chromaticity diagram in which the light emission of the resin molding according to Example 9 is plotted.

[0120] The blackbody locus is also shown in Figure 27. As in Examples 2 to 4, it was found that the white carbon nanoparticle phosphor that emits white light emits light with a deviation of ±0.01 (range of -0.01 to +0.01) from the blackbody locus even when combined with a resin or the like to form a molded product.

[0121] [Example 10] In Example 10, test strips were prepared in which the powder sample of Example 2 was dispersed. FIG. 28 shows the manufacturing procedure and testing of the test strip.

[0122] The powder sample of Example 2 was dispersed in DMSO to prepare a phosphor dispersion liquid (0.3% by mass, 3 mg / mL). Cellulose filter paper (Whatman (registered trademark), cellulose filter) was used as the mount, and the phosphor dispersion liquid was dropped onto three locations, areas 1 to 3, and dried at 80°C to obtain a test paper. Next, light water and heavy water were dropped as test liquids into areas 1 and 3, respectively. Since water was used as the test liquid here, area 2, where nothing was dropped, served as a control. This was irradiated with an ultraviolet lamp, and the light emission was observed. The results are shown in Figure 29.

[0123] FIG. 29 is a diagram showing the state of determination using a test paper.

[0124] 29(A) is a diagram showing the appearance of a test paper in which a phosphor dispersion liquid is dropped onto cellulose filter paper and carbon nanoparticle phosphors are dispersed. The carbon nanoparticle phosphors are contained in three areas, areas 1 to 3.

[0125] Figure 29(B) shows the test paper irradiated with an ultraviolet lamp before the test liquid was added. From Figure 29(B), it can be seen visually that there is no change in the luminescence intensity. Figure 29(C) shows the test paper irradiated with an ultraviolet lamp after the test liquid was added. When irradiated with an ultraviolet lamp, the luminescence intensity of regions 1 and 3, where light water and heavy water were added, respectively, was reduced compared to region 2, which was the control. This demonstrates that the use of the test paper of the present invention makes it possible to easily determine whether a test liquid contains water.

[0126] Next, water containing 0, 2.5, 5, 10, 20, and 100% heavy water by volume was dropped onto the test paper carrying the carbon nanoparticle phosphor, and the emission spectra were measured using a spectrophotometer. The results are shown in Figures 30 and 31.

[0127] FIG. 30 shows emission spectra for various types of water. FIG. 31 is a graph showing the dependence of the luminescence intensity of FIG. 30 on the concentration of heavy water.

[0128] Figure 30 shows the emission spectra when each area of ​​the test paper is irradiated with an excitation wavelength of 370 nm. Figure 30 also shows the emission spectrum of the control (area without water). Figure 30 shows that the emission intensity of the peak near 600 nm decreases as the heavy water content decreases, i.e., as the light water content increases.

[0129] Fig. 31 is a graph in which the emission intensity at an emission wavelength of 600 nm is plotted against the heavy water content. Fig. 31 shows that the emission intensity increases linearly with the heavy water content.

[0130] This can be used to detect light water (H2O) contained in heavy water (D2O) or to determine its amount. This can be used as a simple and inexpensive test paper to detect the amount of light water or heavy water. Furthermore, by using DMSO, DMF, acetonitrile, ethanol, etc. instead of heavy water (D2O), it is possible to determine the presence and amount of light water (H2O) in them. [Industrial Applicability]

[0131] The present invention is advantageous because it allows for the production of carbon nanoparticle phosphors with chromaticity adjustments simply by adjusting the raw materials. Furthermore, light-emitting devices can be provided using such carbon nanoparticle phosphors. In particular, carbon nanoparticle phosphors with specific compositions are excellent phosphors that emit white light with high color rendering properties, making them suitable for use in white light-emitting devices such as white LEDs. Furthermore, because the luminescence intensity of this material is significantly reduced by water, a simple test paper can be provided to measure the amount of water in heavy water, ethanol, or other liquids based on changes in luminescence intensity. [Explanation of symbols]

[0132] 200 Light-emitting device 210, 220 lead wire 230 Alumina substrate 240 Purple light-emitting diode element 250 Gold thin wire 260 Resin molding 270 Resin 300 test papers 310 Inspection Area 320 Mount

Claims

1. A carbon nanoparticle phosphor containing carbon, oxygen, nitrogen, and hydrogen elements, Contains amorphous carbon and graphitic carbon, The nitrogen element includes pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen; the content of the pyridine-type nitrogen is greater than that of the graphite-type nitrogen; The amorphous carbon is in the range of more than 90% by volume to 99% by volume, The graphite carbon satisfies the range of 1% by volume or more and less than 10% by volume, A carbon nanoparticle phosphor, wherein when irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color of light emitted by the carbon nanoparticle phosphor satisfies 0.2≦x<0.3 and 0.25≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates.

2. the amorphous carbon satisfies the range of 95% by volume or more and 99% by volume or less, The carbon nanoparticle phosphor according to claim 1 , wherein the graphite-like carbon is contained in an amount of 1% by volume or more and 5% by volume or less.

3. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are respectively expressed as follows: 0.58≦p≦0.65 0.22≦q≦0.30 0.12≦r<0.16 The carbon nanoparticle phosphor according to claim 1 or 2, which satisfies the above.

4. The carbon element and nitrogen element contents p and q are 0.38<q / p≦0.41 The carbon nanoparticle phosphor according to claim 3 , which satisfies the above.

5. A carbon nanoparticle phosphor containing carbon, oxygen, nitrogen, and hydrogen elements, Contains amorphous carbon and graphitic carbon, The nitrogen element includes pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen; the content of the pyridine-type nitrogen is less than that of the graphite-type nitrogen; the amorphous carbon satisfies the range of 60% by volume or more and 90% by volume or less, the graphite-like carbon satisfies the range of 10% by volume or more and 40% by volume or less, A carbon nanoparticle phosphor, wherein when irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies 0.44≦x≦0.6 and 0.3≦y≦0.45 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates.

6. the amorphous carbon satisfies the range of 60% by volume or more and 83% by volume or less, The carbon nanoparticle phosphor according to claim 5 , wherein the graphite-like carbon satisfies a range of 17% by volume to 40% by volume.

7. The carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (where p+q+r=1) are respectively expressed as follows: 0.58≦p≦0.65 0.15≦q≦0.21 0.19≦r≦0.21 The carbon nanoparticle phosphor according to claim 5 or 6, which satisfies the above.

8. The carbon element and nitrogen element contents p and q are 0.25<q / p<0.34 The carbon nanoparticle phosphor according to claim 7 , which satisfies the above.

9. The carbon nanoparticle phosphor according to any one of claims 1 to 8, wherein the carbon nanoparticle phosphor has a diameter in the range of 1 nm to 20 nm.

10. A light emitting device comprising at least an excitation source and a phosphor, A light emitting device, wherein the phosphor comprises the carbon nanoparticle phosphor according to any one of claims 1 to 9.

11. The light emitting device according to claim 10 , wherein the phosphor is a resin molded body in which the carbon nanoparticle phosphor is dispersed.

12. A test paper for determining whether a test liquid contains water, The test paper contains carbon, oxygen, nitrogen, and hydrogen elements, and also contains amorphous carbon and graphite-like carbon, and the nitrogen element contains a carbon nanoparticle fluorescent material containing pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen.

13. A method for producing the carbon nanoparticle phosphor according to claim 1, comprising: preparing a raw material solution by dissolving at least a carbon source in an organic solvent; heating the raw material solution; It encompasses The method wherein the organic solvent is a nitrogen-containing organic solvent.

14. The method described in claim 13, wherein the concentration of the carbon source in the organic solvent is in the range of 0.05 mol / L or more and 0.2 mol / L or less.

15. A method for producing the carbon nanoparticle phosphor according to claim 5, comprising: preparing a raw material solution by dissolving at least a carbon source in an organic solvent; heating the raw material solution; It encompasses the organic solvent is formamide; The method wherein the preparing step further comprises dissolving at least one nitrogen source selected from the group consisting of ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine in the organic solvent.

16. The concentration of the carbon source in the organic solvent satisfies the range of 0.05 mol / L or more and 0.2 mol / L or less, The method according to claim 15, wherein the concentration of the nitrogen source in the organic solvent satisfies the range of 0.05 mol / L to 3.0 mol / L.

17. A method according to any one of claims 13 to 16, wherein the carbon source is at least one selected from the group consisting of citric acid, citric acid monohydrate, ammonium citrate, benzoic acid, ascorbic acid, glucose, fructose, and sucrose.

18. A method for producing a color-tuned carbon nanoparticle phosphor, comprising: The carbon nanoparticle phosphor contains carbon, oxygen, nitrogen, and hydrogen elements, and includes amorphous carbon and graphite carbon, and the nitrogen element includes pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, and graphite-type nitrogen; the content of the pyridine-type nitrogen is less than that of the graphite-type nitrogen, the amorphous carbon is in the range of 45 vol% to 70 vol%, and the graphite-like carbon is in the range of 30 vol% to 55 vol%, When irradiated with light having a wavelength in the range of 300 nm to 380 nm, the color emitted by the carbon nanoparticle phosphor satisfies 0.3≦x<0.44 and 0.3≦y≦0.4 in terms of the (x, y) values ​​on the CIE 1931 chromaticity coordinates; preparing a raw material solution by dissolving at least a carbon source in an organic solvent; heating the raw material solution; It encompasses the organic solvent is formamide; The preparing step includes dissolving a nitrogen source, which is ethylenediamine, in the organic solvent; the carbon source is citric acid; the concentration of the carbon source in the organic solvent satisfies the range of 0.05 mol / L or more and 0.2 mol / L or less; The method, wherein the concentration of the nitrogen source in the organic solvent satisfies the range of 0.05 mol / L to 1.5 mol / L.

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