JP2023149319A - Phosphor, manufacturing method thereof, and, light-emitting device therewith - Google Patents

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

Application for application of Article 30, Paragraph 2 of the Patent Act (1) Published on November 27, 2021, published by Japan Society of Surface and Vacuum Science, The 9th International Symposium on Surface Science (ISSS-9) Lecture Proceedings, 01PS -43 P. 360 (2) The 9th International Symposium on Surface Science (ISSS-9) will be held from November 28th to December 1st, 2021, sponsored by the Japan Society of Surface and Vacuum Science.

The present invention relates to a phosphor, a method for manufacturing the same, and a light emitting device using the same. Specifically, the present invention relates to a phosphor using carbon nanoparticles, a method for manufacturing the same, and a light emitting device using the same.

In recent years, compositions containing carbon nanoparticle phosphors that emit blue to red light upon irradiation with excitation light have been developed (see, for example, Patent Document 1). According to Patent Document 1, 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 a water-soluble solvent. a step of hydrothermally synthesizing the solution obtained by the hydrothermal synthesis step, a step of adding alcohol to the solution obtained by the hydrothermal synthesis step and stirring it, and a step of extracting the supernatant liquid of the solution obtained by the adding and stirring step. Provided is a composition containing a carbon nanoparticle phosphor that emits blue to red light upon irradiation with excitation light. The emission wavelength of such a carbon nanoparticle phosphor has no wavelength dependence on excitation light, and a desired emission wavelength can be selectively obtained. However, adjustment (tuning) of chromaticity has been difficult.

Furthermore, a graphene quantum dot phosphor has been reported (see, for example, Non-Patent Document 1). According to Non-Patent Document 1, a nitrogen-doped graphene quantum dot phosphor is produced by hydrothermal synthesis using citric acid and ethylenediamine, and that the emission wavelength changes as the wavelength of incident light changes. report. However, chromaticity cannot be adjusted.

International Publication No. 2018/163955

Dan Qu et al., SCIENTIFIC REPORTS 4, 5294, 2014

An object of the present invention is 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 The purpose is to provide test strips using the same.

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. This solves the above 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 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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< 0.3 and 0.25≦y≦0.4, the organic solvent is a nitrogen-containing organic solvent,
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< 0.44 and 0.3≦y≦0.4, the organic solvent is formamide and/or N-methylformamide, and the preparation includes adding ethylenediamine (EDA) to the organic solvent. ), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), and at least one nitrogen source selected from the group consisting of cysteamine. further dissolve,
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 is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. 0.6 and 0.3≦y≦0.45, the organic solvent is formamide, and the preparing includes ammonium hydroxide, o-phenylenediamine, and p- At least one nitrogen source selected from the group consisting of phenylene diamine may be further dissolved.
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< 0.3 and 0.25≦y≦0.4, 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,
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< 0.44 and 0.3≦y≦0.4, 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 carbon source in the organic solvent The concentration of the nitrogen source satisfies a 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 or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. 0.6 and 0.3≦y≦0.45, 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 may satisfy a range of 0.05 mol/L or more and 3.0 mol/L 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 satisfies the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< 0.3 and 0.25≦y≦0.4, 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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< 0.44 and 0.3≦y≦0.4, the organic solvent is formamide, and 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 or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. 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 include heating the raw material solution at a temperature of 150° C. or more and 230° C. or less for a period of 5 hours or more and 15 hours or less.
The method may further include collecting a product produced by heating the raw material solution and heating it in vacuum.
The heating in vacuum may include heating the product at a degree of vacuum of 1 Pa or more and 10,000 Pa or less, for a time of 50° C. or more and 70° C. or less, and for a time of 30 minutes or more and 12 hours or less.
The carbon nanoparticle phosphor containing carbon element, oxygen element, nitrogen element, and hydrogen element according to the present invention contains amorphous carbon and graphitic carbon, and the nitrogen element includes pyridine nitrogen, amide nitrogen, Contains pyrrole-type nitrogen and graphite-type nitrogen, thereby solving the above problems.
The content of the pyridine-type nitrogen is greater than that of the graphite-type nitrogen, the amorphous carbon satisfies a range of greater than 90% by volume and less than or equal to 99% by volume, and the content of graphitic carbon is greater than or equal to 1% by volume and less than or equal to 10% by volume. % and has a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is the value of (x, y) on the CIE 1931 chromaticity coordinates. 0.2≦x<0.3 and 0.25≦y≦0.4 may be satisfied.
The amorphous carbon may satisfy a range of 95 volume % or more and 99 volume % or less, and the graphitic carbon may satisfy a range of 1 volume % or more and 5 volume % or less.
The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.58≦p≦0.65
0.22≦q≦0.30
0.12≦r<0.16
may be satisfied.
The contents p and q of the carbon element and nitrogen element are:
0.38<q/p≦0.41
may be satisfied.
The content of the pyridine-type nitrogen is lower than that of the graphite-type nitrogen, the amorphous carbon satisfies a range of 45 volume% to 70 volume%, and the graphitic carbon content is 30 volume% to 55 volume%. When irradiated with light that satisfies the following range and has a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is determined by the (x, y) value on the CIE 1931 chromaticity coordinates. 0.3≦x<0.44 and 0.3≦y≦0.4 may be satisfied.
The amorphous carbon may satisfy a range of 53 volume % or more and 68 volume % or less, and the graphitic carbon may satisfy a range of 32 volume % or more and 47 volume % or less.
The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.57≦p≦0.65
0.20≦q<0.26
0.16≦r<0.19
may be satisfied.
The contents p and q of the carbon element and nitrogen element are:
0.32<q/p<0.44
may be satisfied.
The content of the pyridine type nitrogen is lower than that of the graphite type nitrogen, the amorphous carbon satisfies a range of 60 volume % to 90 volume %, and the graphitic carbon content is 10 volume % to 40 volume %. When irradiated with light that satisfies the following range and has a wavelength in the range of 300 nm or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is determined by the (x, y) value on the CIE1931 chromaticity coordinates. 0.44≦x≦0.6 and 0.3≦y≦0.45 may be satisfied.
The amorphous carbon may satisfy a range of 60 volume % or more and 83 volume % or less, and the graphitic carbon may satisfy a range of 17 volume % or more and 40 volume % or less.
The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.58≦p≦0.65
0.15≦q≦0.21
0.19≦r≦0.21
may be satisfied.
The contents p and q of the carbon element and nitrogen element are:
0.25<q/p<0.34
may be satisfied.
The carbon nanoparticle phosphor may have a diameter ranging from 1 nm to 20 nm. A light emitting device according to the present invention includes at least an excitation source and a phosphor, and the phosphor includes the above-described carbon nanoparticle phosphor, thereby solving the above problem.
The phosphor may be a resin molded body in which the carbon nanoparticle phosphor is dispersed.
A test paper for determining whether a test liquid contains water according to the present invention contains the above-mentioned carbon nanoparticle phosphor, thereby solving the above problem.

The method for producing a carbon nanoparticle phosphor with adjusted chromaticity of the present invention includes preparing a raw material solution in which at least a carbon source is dissolved in an organic solvent, heating the raw material solution, and The chromaticity can be adjusted (tuned) by appropriately selecting the type and concentration of the source, the type of organic solvent, and further the type and concentration of the nitrogen source. The carbon nanoparticle phosphor of the present invention contains a carbon element, an oxygen element, a nitrogen element, and a hydrogen element, and contains amorphous carbon and graphitic carbon, and the nitrogen element is pyridine nitrogen, amide nitrogen , pyrrole-type nitrogen, and graphite-type nitrogen. The chromaticity can be adjusted by adjusting the ratio of amorphous carbon and graphitic carbon and controlling the composition ratio using the above method. By using such a phosphor, it is possible to provide a light-emitting device that has chromaticity near the blackbody locus and generates light that is relatively similar to natural light. Since the luminescent intensity of the phosphor of the present invention decreases relative to water, it is possible to provide a test paper for determining whether or not a liquid contains water based on a change in luminescent intensity.

A diagram showing a flow for manufacturing a carbon nanoparticle phosphor with adjusted chromaticity according to the present invention Schematic diagram showing a light emitting device using the carbon nanoparticle phosphor of the present invention Schematic diagram showing a test paper using the carbon nanoparticle phosphor of the present invention Diagram showing the reaction formula of Example 1 and the state of light emission of the liquid sample of Example 1 A diagram showing the reaction formulas of Examples 2 to 6 and the state of light emission of the liquid samples of Examples 2 to 6. A diagram showing the reaction formulas of Examples 7 and 8 and the state of light emission of the liquid samples of Examples 7 and 8. Diagram showing the XRD patterns of powder samples of Example 1, Example 2 and Example 7 Diagram showing TEM images of the liquid sample of Example 1 at various magnifications Diagram showing TEM images of the liquid sample of Example 2 at various magnifications Diagrams showing TEM images of the liquid sample of Example 7 at various magnifications Diagram showing XPS spectra of liquid samples of Example 1, Example 2 and Example 7 Diagram showing the deconvoluted HRXPS spectrum of the liquid sample of Example 1 Diagram showing the deconvoluted HRXPS spectrum of the liquid sample of Example 2 Diagram showing the deconvolved HRXPS spectrum of the liquid sample of Example 7 Diagram showing changes in the amount of nitrogen doping centers calculated from FIGS. 12 to 14 Diagram showing ATR-FTIR spectra of liquid samples of Example 1, Example 2, and Example 7 Diagram showing absorption spectra of liquid samples of Example 1, Example 2 and Example 7 Diagram showing emission spectra of liquid samples of Example 1, Example 2, and Example 7 Diagram showing absorption spectra of liquid samples of Examples 3 and 4 Diagram showing absorption spectra of liquid samples of Examples 5 and 6 CIE chromaticity diagram plotting the luminescence of the liquid samples of Examples 1 to 8 Diagram showing two-dimensional luminescence mapping of the liquid sample of Example 1 Diagram showing two-dimensional luminescence mapping of the liquid sample of Example 2 Diagram showing two-dimensional luminescence mapping of the liquid sample of Example 7 Diagram showing the appearance of a resin molded article according to Example 9 Diagram showing the fluorescence spectrum of the resin molded article according to Example 9 CIE chromaticity diagram plotting the luminescence of the resin molded body according to Example 9 Diagram showing test strip manufacturing procedure and testing Diagram showing how judgments are made using test strips Diagram showing emission spectra for various types of water Diagram showing the dependence of luminescence intensity on heavy water concentration in Figure 30

Embodiments of the present invention will be described below with reference to the drawings. Note that similar elements are given similar numbers and their explanations will be omitted.

(Embodiment 1)
In Embodiment 1, a method of manufacturing a carbon nanoparticle phosphor with adjusted (tuned) chromaticity of the present invention and a carbon nanoparticle phosphor obtained thereby will be described.

FIG. 1 is a diagram showing a flow for manufacturing a carbon nanoparticle phosphor with adjusted chromaticity according to the present invention.

Step S110: Prepare a raw material solution in which at least a carbon source is dissolved in an organic solvent.
Step S120: Heating the raw material solution.
The present inventors have discovered that carbon nanoparticle phosphors can be obtained simply by heating a carbon source using an organic solvent rather than by hydrothermal synthesis. Through experiments, we have found that by appropriately selecting the type and, furthermore, the type and concentration of the nitrogen source, the chromaticity can be adjusted along the blackbody locus. Each step will be explained in detail.

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

The organic solvent used in step S110 is not particularly limited, but preferably one containing nitrogen can be used. By containing nitrogen, a nitrogen-doped carbon nanoparticle phosphor can be obtained. Such organic solvents include formamide and/or N-methylformamide. These are preferred because they can dissolve the carbon source mentioned above.

In step S110, a raw material solution may be prepared in which, in addition to the carbon source described above, a nitrogen source is further dissolved in an organic solvent. This allows the amount of nitrogen doping to be controlled. Such nitrogen sources include ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), cysteamine, hydroxylated Examples include ammonium, o-phenylenediamine, and p-phenylenediamine. These can be dissolved in organic solvents and enable doping with pyridine-type nitrogen, amide-type nitrogen, pyrrole-type nitrogen, graphite-type nitrogen, and the like.

Amorphous carbon and graphitic carbon can be generated by step S120. Here, the heating is not particularly limited as long as the carbon source is decomposed and the carbon reacts with nitrogen in the organic solvent or nitrogen in the nitrogen source, but preferably, the raw material solution is heated at a temperature of 150°C or higher and 230°C or lower. Heat at a temperature of 5 hours or more and 15 hours or less. Under these conditions, the reaction proceeds efficiently and a carbon nanoparticle phosphor can be obtained. Heating is more preferably performed at a temperature of 170° C. or higher and 210° C. or lower for a period of 7 hours or more and 10 hours or less.

In this way, the carbon nanoparticle phosphor is obtained in a state dispersed in the solvent, but when the carbon nanoparticle phosphor is obtained in powder form, the obtained product is It may be collected by centrifugation or the like and heated in vacuum.

Preferably, the product is heated at a degree of vacuum of 1 Pa or more and 10,000 Pa or less, for a time of 50° C. or more and 70° C. or less, for a period of 30 minutes or more and 12 hours or less. Thereby, the product can be efficiently recovered.

By selecting a carbon source, an organic solvent, and, if necessary, a nitrogen source, and adjusting their concentrations, the inventors of the present application have discovered that the chromaticity can be adjusted, and the carbon nanoparticle fluorescence on or near the blackbody locus can be adjusted. I discovered that I could donate my body. For ease of understanding, carbon nanoparticle phosphors adjusted to such chromaticity will be referred to as cyan, white, and orange carbon nanoparticle phosphors, and methods for producing these phosphors will be explained. do.

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

In this case, in step S110, it is only necessary to prepare a raw material solution in which the above-mentioned carbon source is dissolved in an organic solvent containing nitrogen. As a result, the content of pyridine-type nitrogen is higher than that of graphite-type nitrogen, and the content of amorphous carbon satisfies the range of more than 90 volume% and 99 volume% or less, and the range of 1 volume% or more and less than 10 volume%. It contains graphitic carbon and can meet the above-mentioned emission colors. Here, the total amount of amorphous carbon and graphitic carbon is 100% by volume.

More preferably, the concentration of the carbon source in the organic solvent satisfies a range of 0.05 mol/L or more and 0.2 mol/L or less. Within this range, the cyan-based carbon nanoparticle phosphor containing amorphous carbon that satisfies the range of 95 volume % or more and 99 volume % or less and graphitic carbon that satisfies the range of 1 volume % or more and 5 volume % or less is used. can get.

Preferably, the concentration of the carbon source in the organic solvent satisfies a 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, it satisfies a predetermined compositional formula to be described later, and the deviation (Duv) from the blackbody locus in the chromaticity coordinates can be suppressed within the range of ±0.03. Note that the deviation from the blackbody locus was evaluated according to the evaluation method disclosed in JIS Z8725.

<White type>
A white 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 a color that corresponds to (x, y) on the CIE 1931 chromaticity coordinates. The values satisfy 0.3≦x<0.44 and 0.3≦y≦0.4.

In this case, in step S110, the above-mentioned carbon source is dissolved in formamide and/or N-methylformamide as an organic solvent, and ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, A raw material solution may be prepared in which at least one nitrogen source selected from the group consisting of ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA), and cysteamine is further dissolved. . As a result, the content of pyridine-type nitrogen is lower than that of graphite-type nitrogen, and satisfies the range of amorphous carbon from 45 volume% to 70 volume% and from 30 volume% to 55 volume%. A white carbon nanoparticle phosphor containing graphitic carbon is obtained. Here, the total amount of amorphous carbon and graphitic carbon is 100% by volume.

More preferably, the concentration of the carbon source in the organic solvent satisfies a 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 a range of 0.05 mol/L or more and 1 Satisfies the range of .5 mol/L or less. Within this range, a white carbon nanoparticle phosphor containing amorphous carbon that satisfies the range of 53 volume % to 68 volume % and graphitic carbon that satisfies the range of 32 volume % to 47 volume % is used. can get.

Preferably, the concentration of the carbon source in the organic solvent satisfies a range of 0.1 mol/L or more and 0.15 mol/L or less, and the concentration of the nitrogen source in the organic solvent satisfies a range of 0.05 mol/L or more and 1 Satisfies the range of .0 mol/L or less. Within this range, a white carbon nanoparticle phosphor can be efficiently obtained.

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, it is possible to satisfy a predetermined compositional formula, which will be described later, and to suppress the deviation from the blackbody locus in the chromaticity coordinates to a range of ±0.01.

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

In this case, in step S110, the above-mentioned carbon source is dissolved in formamide as an organic solvent, and at least one selected from the group consisting of ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine is added. A raw material solution in which a nitrogen source is further dissolved may be prepared. As a result, the content of pyridine-type nitrogen is lower than that of graphite-type nitrogen, and satisfies the range of amorphous carbon from 60 volume% to 90 volume% and from 10 volume% to 40 volume%. An orange carbon nanoparticle phosphor containing graphitic carbon is obtained. Here, the total amount of amorphous carbon and graphitic carbon is 100% by volume.

More preferably, the concentration of the carbon source in the organic solvent satisfies a 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 a range of 0.05 mol/L or more and 3 Satisfies the range of .0 mol/L or less. In this range, an orange carbon nanoparticle phosphor containing amorphous carbon that satisfies the range of 77 volume% or more and 83 volume% or less and graphitic carbon that satisfies the range of 17 volume% or more and 23 volume% or less is used. can get.

Preferably, the concentration of the carbon source in the organic solvent satisfies a range of 0.1 mol/L or more and 0.15 mol/L or less, and the concentration of the nitrogen source in the organic solvent satisfies a range of 0.5 mol/L or more and 2 Satisfies the range of .5 mol/L or less. Within this range, an orange carbon nanoparticle phosphor can be efficiently obtained. Even more preferably, the concentration of the nitrogen source in the organic solvent satisfies a range of 0.5 mol/L or more and 1 mol/L or less.

More preferably, the organic solvent is formamide, the carbon source is citric acid, and the nitrogen source is ammonium hydroxide. In this case, it is possible to satisfy a predetermined compositional formula, which will be described later, and to suppress the deviation from the blackbody locus in the chromaticity coordinates to a range of ±0.01.

Next, the carbon nanoparticle phosphor of the present invention obtained in this manner will be explained.
The nanoparticle phosphor of the present invention has carbon as a main component, but contains carbon element, oxygen element, nitrogen element, and hydrogen element by using the above-mentioned raw material solution. Here, the main component carbon includes amorphous carbon and graphitic carbon, and by controlling the amounts of these carbons, the color, chromaticity, and color temperature of the emitted light can be controlled. Amorphous carbon is non-crystalline carbon, and graphitic carbon is crystalline carbon. If a broad peak is observed near 2θ = 20.5° in powder X-ray diffraction, amorphous carbon is present, and if a sharp peak is observed near 2θ = 27°, it is graphite-like. It can be determined that carbon is present.

The nanoparticle phosphor of the present invention contains pyridine nitrogen, amide nitrogen, pyrrole nitrogen, and graphite nitrogen as nitrogen elements. Emission color, chromaticity, and color temperature can be controlled by controlling these contents. Here, pyridine type nitrogen, amide type nitrogen, pyrrole type nitrogen, and graphite type nitrogen are represented by the structural formula shown in the following 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 may be collectively called a nitrogen doping center.

The inventors of the present application have found that a carbon nanoparticle phosphor can be obtained by the above-described manufacturing method, and in particular, by controlling the amounts of amorphous carbon and graphitic carbon, the quantitative relationship of nitrogen doping centers, and the composition, We have discovered that the chromaticity is adjusted and that the carbon nanoparticle phosphor is on or near the blackbody locus. For ease of understanding, carbon nanoparticle phosphors with adjusted chromaticity will be referred to as cyan-based, white-based, and orange-based carbon nanoparticle phosphors, and these phosphors will be described.

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

In this case, the content of pyridine-type nitrogen is greater than that of graphite-type nitrogen. Further, assuming that the total amount of amorphous carbon and graphitic carbon is 100% by volume, the cyan-based carbon nanoparticle phosphor contains amorphous carbon that satisfies a range of greater than 90% by volume and less than or equal to 99% by volume, and 1% by volume or more and 10% by volume or less. Contains graphitic carbon that satisfies the range of less than % by volume. It exhibits cyan-based light emission due to a significant increase in amorphous carbon. The content of amorphous carbon and graphitic carbon is calculated from the intensity ratio of peaks at 2θ=20.5° and 27° in powder X-ray diffraction.

The cyan-based carbon nanoparticle phosphor more preferably contains amorphous carbon that satisfies a range of 95% to 99% by volume, and graphitic carbon that satisfies a range of 1% to 5% by volume. This makes it possible to obtain a phosphor with good color purity.

In the cyan-based carbon nanoparticle phosphor, preferably the carbon element content p (atomic %), the nitrogen element content q (atomic %), and the oxygen element content r (atomic %) (however, p + q + r = 1 ) are respectively,
0.58≦p≦0.65
0.22≦q≦0.30
0.12≦r<0.16
satisfy. Thereby, the deviation from the blackbody locus in the chromaticity coordinates can be suppressed within the range of ±0.03. More preferably, the contents p and q satisfy 0.38<q/p≦0.41.

<White type>
A white 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 a color that corresponds to (x, y) on the CIE 1931 chromaticity coordinates. The values satisfy 0.3≦x<0.44 and 0.3≦y≦0.4.

In this case, the content of pyridine-type nitrogen is lower than that of graphite-type nitrogen, and the white carbon nanoparticle phosphor contains amorphous carbon that satisfies the range of 45% by volume to 70% by volume, and 30% by volume. It contains graphitic carbon that satisfies the range of 55% by volume or less. Further, the content of amorphous carbon is higher than that of graphitic carbon. Here, the total amount of amorphous carbon and graphitic carbon is 100% by volume.

The white carbon nanoparticle phosphor more preferably contains amorphous carbon that satisfies the range of 53 volume % or more and 68 volume % or less, and graphitic carbon that satisfies the range of 32 volume % or more and 47 volume % or less. This makes it possible to emit blue-white, white, and warm white light.

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 %) (however, p + q + r = 1 ) are respectively,
0.57≦p≦0.65
0.20≦q<0.26
0.16≦r<0.19
satisfy. Thereby, the deviation from the blackbody locus in the chromaticity coordinates can be suppressed within the range of ±0.01. More preferably, the contents p and q satisfy 0.32<q/p<0.44.

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

In this case, the content of pyridine-type nitrogen will be less than that of graphite-type nitrogen. The orange carbon nanoparticle phosphor contains amorphous carbon that satisfies the range of 60 volume % or more and 90 volume % or less, and graphitic carbon that satisfies the range of 10 volume % or more and 40 volume % or less. Here, the total amount of amorphous carbon and graphitic carbon is 100% by volume.

The orange carbon nanoparticle phosphor more preferably contains amorphous carbon that satisfies the range of 60 volume % or more and 83 volume % or less, and graphitic carbon that satisfies the range of 17 volume % or more and 40 volume % or less. This makes it possible to emit light with good color purity.

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 respectively,
0.58≦p≦0.65
0.15≦q≦0.21
0.19≦r≦0.21
satisfy. Thereby, the deviation from the blackbody locus in the chromaticity coordinates can be suppressed within the range of ±0.01. More preferably, the contents p and q satisfy 0.25<q/p<0.34.

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

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 or more and 380 nm or less, but when the wavelength of the excitation light changes, the emission wavelength also changes. . That is, when 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 or more and 380 nm or less, the (x, y) value on the CIE1931 chromaticity coordinate is 0.3≦x<0. .44 and 0.3≦y≦0.4, and emits white light, but when the wavelength of excitation light is 450 nm, it emits green light, and when the wavelength of excitation light is 525 nm, it emits yellow-green light. When the wavelength of light is 550 nm, it emits orange light, and when the wavelength of excitation light is 600 nm, it emits red light.

The carbon nanoparticle phosphor of the present invention is composed of nanoparticles having a particle size on the nano-order, and preferably has a diameter in the range of 1 nm to 20 nm. Within this range, luminous efficiency is high.

The carbon nanoparticle phosphor of the present invention has functional groups and bonds such as -OH, -CONH ₂ , C=O, -COOH, C=C, O-C=O, C-H, and N-H. It's okay. This enables highly efficient visible light emission. These bonds are confirmed by infrared absorption spectra.

The carbon nanoparticle phosphor of the present invention may be dispersed in a solvent, resin, or the like. This reduces the influence of concentration quenching and increases luminous efficiency. Such a solvent may be, for example, dimethyl sulfoxide (DMSO), dimethylformamide, etc. in addition to the organic solvent used in the synthesis, or may be water. The resin may be any water-soluble polymer that transmits light having wavelengths from the ultraviolet region to the visible region, such as polyvinyl alcohol, sodium polyacrylate, polyacrylamide, polyethyleneimine, polyethylene oxide, polyvinylpyrrolidone, and carboxyl vinyl polymer. You can choose. With such a resin, it is possible to provide a resin molded body such as a thin film by spin coating or dripping, a bulk body by drying, and a fiber by electrospinning. Such a resin molded body is easy to handle.

When dispersed in a solvent, resin, etc., the content of the carbon nanoparticle phosphor is preferably in the range of 0.01% by mass or more and 5% by mass or less. Within this range, high emission intensity and high quantum efficiency can be expected. More preferably, the content of the carbon nanoparticle phosphor is in the range of 0.01% by mass or more and 1% by mass or less.

(Embodiment 2)
In Embodiment 2, 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.

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 such a configuration, it is possible to provide a light emitting device that emits light of a desired color.

The excitation source may be a light emitting diode, a laser diode, an organic EL, a semiconductor laser, a fluorescent lamp, etc., and one that emits light having a peak in the range of 200 nm or more and 600 nm or less is used. Among these, a violet light emitting diode having a peak in the range of 330 nm or more and 420 nm or less is preferable because it can efficiently excite the carbon nanoparticle phosphor of the present invention.

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

The violet light emitting diode element 240 is covered with a resin molded body 260 in which the carbon nanoparticle phosphor of the present invention is dispersed in resin. Here, a white carbon nanoparticle phosphor is used as the carbon nanoparticle phosphor. A wall member 280 made of white silicone resin or the like is provided on the alumina substrate 230, and a violet light emitting diode element 240 covered with a resin molded body 260 is located in the center thereof. In the center of the wall member 280, the violet light emitting diode element 240 covered with the resin molded body 260 is sealed with a transparent resin 270 such as epoxy resin.

When the lead wires 210 and 220 of the light emitting device 200 are energized, the violet light emitting diode element 240 emits light having a peak wavelength of 405 nm. This light enters the resin molded body 260 of the present invention, and the carbon nanoparticle phosphor within the resin molded body 260 is excited to emit white light. The white light passes through the resin 270 and exits to the outside. In this way, the light emitting device 200 functions to emit white light.

Here, the resin molded body 260 is configured to cover the violet light emitting diode element 240, but is not limited thereto. For example, the resin molded body 260 may be placed on the light emitting surface of the violet light emitting diode element 240 or may be placed on the resin 270. Alternatively, instead of the resin 270, the entire resin molded body 260 may be used.

In addition, although the resin molded body 260 has been described here as containing only a carbon nanoparticle phosphor that emits white light as a phosphor, it may also contain a cyan carbon nanoparticle phosphor or an orange carbon nanoparticle phosphor. Needless to say, it's okay. Further, instead of the violet light emitting diode element, a wavelength tunable laser may be used to provide a light emitting device that can change the color from white to red. Such modifications are also within the scope of this invention.

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 be employed in a bullet type white light emitting diode lamp. Such modifications can be easily made by those skilled in the art.

(Embodiment 3)
In Embodiment 3, a test paper using the carbon nanoparticle phosphor of the present invention will be described.
The inventors of the present invention have discovered that when the carbon nanoparticle phosphor of the present invention comes into contact with water (H ₂ O) or heavy water (D ₂ O), the emission intensity thereof decreases. Utilizing such characteristics, it is possible to provide a test paper that easily determines whether a test liquid contains water (H ₂ O) or heavy water (D ₂ O).

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

The test strip 300 consists of a mount 320 having a test area 310. Inspection area 310 contains the carbon nanoparticle phosphor described in Embodiment 1. The mount 320 is not particularly limited as long as it is paper that can disperse and support the carbon nanoparticle phosphor, but is preferably cellulose fiber. Cellulose fibers have surface functional groups such as -OH and -COOH, which can adsorb carbon nanoparticle phosphors and prevent them from aggregating with each other. Therefore, by using cellulose fibers, it is possible to provide a test paper that suppresses concentration quenching, has excellent luminescence intensity, and can be easily determined visually.

Although six inspection areas 310 are shown in FIG. 3, the inspection area may be the entire mount. The separation is advantageous for simultaneous discrimination of multiple test solutions. Note that such a test paper 300 is manufactured by dropping a composition in which carbon nanoparticle phosphors are dispersed onto a mount 320 and drying the composition.

Next, a method of determining whether or not a test liquid contains water using such a test paper 300 will be explained. Here, the water may be light water (H ₂ O) or heavy water (D ₂ O). First, a liquid that does not contain water is dropped onto one area of the test area 310 of the test strip 300 as a control. Next, the test liquid is dropped onto another area, irradiated with an excitation source, and the state of light emission is observed. If there is a test region where the luminescence intensity is visually lower than that of the control, it can be determined that the test liquid in that region contains water.

The luminescence intensity decreases linearly depending on the water content, so if the relationship between the water content and the luminescence intensity is maintained in advance, the water content can be determined by measuring the luminescence spectrum. can.

Furthermore, the emission intensity of the carbon nanoparticle phosphor of the present invention also differs depending on whether it is 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. Utilizing these characteristics, the content of light water and heavy water in the test liquid can be determined.

Next, the present invention will be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

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

In detail, under the conditions shown in Table 1, citric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was used as a carbon source, and ethylenediamine (EDA, manufactured by Sigma-Aldrich, purity >99.5%, specific gravity) was used as a nitrogen source as needed. D = 0.899 g/mL), dimethylamine (DEA, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), urea (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), and ammonium hydroxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). was dissolved in formamide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) as an organic solvent to prepare a raw material solution (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).

The obtained product was centrifuged (rotation speed: 800 rpm) and washed several times with Milli-Q water and ethanol. The washed product was dried in vacuum (degree of vacuum: 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, manufactured by Fuji Film 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% by weight (0.025 mg/mL). In this way, liquid samples of Examples 1 to 8 were obtained.

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

FTIR spectra of the liquid samples of Examples 1 to 8 were obtained by total reflection infrared spectroscopy (ATR-FTIR) using a spectrophotometer (Nicolet iS50 FTIR, manufactured by Thermo Scientific). The cumulative number of measurements was 50. The results are shown in FIG. The absorption spectra of the liquid samples of Examples 1 to 8 were measured using an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V-570). The results are shown in FIG. The emission spectra of the liquid samples of Examples 1 to 8 were measured using a spectrofluorescence altimeter (manufactured by JASCO Corporation, FP-8500). CIE chromaticity (x, y) was calculated from the emission spectrum. These results are shown in FIGS. 18 to 24. These results will be summarized and explained.

FIG. 4 is a diagram showing the reaction formula of Example 1 and the state of light emission of the liquid sample of Example 1.
FIG. 5 is a diagram showing the reaction formulas of Examples 2 to 6 and the state of light emission of the liquid samples of Examples 2 to 6.
FIG. 6 is a diagram showing the reaction formulas of Examples 7 and 8 and the state of light emission of the liquid samples of Examples 7 and 8.

Although shown in gray scale in FIGS. 4 to 6, according to FIG. 4, when the liquid sample of Example 1 was irradiated with an ultraviolet lamp, it was found that it emitted blue (cyan) light. According to FIG. 5, when the liquid samples of Examples 2 to 6 were irradiated with an ultraviolet lamp, it was found that they emitted blue-white to white to warm white (white type). According to FIG. 6, when the liquid samples of Examples 7 and 8 were irradiated with an ultraviolet lamp, it was found that they emitted orange (orange-based) light. From this, it was shown that by implementing the method shown in FIG. 1, a composition (phosphor) that emits fluorescence can be obtained. Furthermore, as shown in Table 1, it was shown that the color of the emitted light could be changed by selecting the nitrogen source and concentration.

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

According to FIG. 7, all XRD patterns show a broad peak near 2θ=20.5° and a sharp peak near 2θ=27°, indicating that amorphous carbon and graphitic carbon are the main components. I found out that it does. Although not shown, the powder samples of Examples 3-6 and 8 also showed similar patterns. The volume percentages of amorphous carbon and graphitic carbon were calculated from these peak intensity ratios. The results are shown in Table 2.

According to Table 2, the content of amorphous carbon is higher than that of graphitic carbon, but it can be seen that the content differs depending on the emission color. Phosphors that emit cyan light contain a very small amount of graphitic carbon and a significant amount of amorphous carbon, while phosphors that emit white light contain a relatively large amount of amorphous carbon, although graphitic carbon is also relatively present. There is a tendency for phosphors that emit orange light to have a small amount of graphitic carbon and a large amount of amorphous carbon.

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.

According to FIG. 8, a layered structure derived from amorphous carbon was confirmed as shown by the dotted line. Furthermore, when the circled area was enlarged, lattice fringes were observed, indicating that it was crystalline graphite-like carbon. According to FIGS. 9 and 10, many nanoparticles indicated by black spots were confirmed, and the particle size was found to be in the range of 1 nm to 20 nm. The particle size is the average value obtained by obtaining a transmission image using a transmission electron microscope (TEM) at a magnification of 1000 times or more and measuring the particle size of at least 100 nanoparticles in an arbitrary 500 nm square area. . Since nanoparticles are not perfectly spherical, the longest diameter is taken as the particle size of the nanoparticle. From the above, it was shown that carbon nanoparticle phosphors were dispersed in the liquid sample.

FIG. 11 is a diagram showing XPS spectra of liquid samples of Examples 1, 2, and 7.

According to FIG. 11, it was found that carbon element, oxygen element, and nitrogen element were present in the carbon nanoparticle phosphors in the liquid samples of Examples 1, 2, and 7. Note that in the XPS spectrum, peaks due to elements in the solvent (DMSO) are removed. The liquid samples of Examples 3-6 and 8 showed similar XPS spectra.

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%) (however, p+q+r=1), respectively,
0.58≦p≦0.65
0.22≦q≦0.30
0.12≦r<0.16
If the conditions are met, blue (cyan) light is emitted,
0.57≦p≦0.65
0.20≦q<0.26
0.16≦r<0.19
If the conditions are satisfied, blue-white to white to warm white (white) light is emitted,
0.58≦p≦0.65
0.15≦q≦0.21
0.19≦r≦0.21
It was shown that when the conditions are satisfied, orange light is emitted.

FIG. 12 shows a deconvolved 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 deconvolved HRXPS spectrum of the liquid sample of Example 7.

12 to 14 all show the results of deconvolution of the N-1s peak of the XPS spectrum shown in FIG. 11. According to FIGS. 12 to 14, it was found that four main peaks were shown, corresponding to binding energies of 398.7 eV, 399.6 eV, 400.3 eV, and 401.3 eV, respectively. From this, these were the types of nitrogen doping centers in 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 Example 8 were also similar.

FIG. 15 is a diagram showing changes in the amount of nitrogen doping centers calculated from FIGS. 12 to 14.

According to FIG. 15, it can be seen that the quantitative relationship of nitrogen doping centers differs depending on the emission color. In particular, the relationship between pyridine-type nitrogen and graphite-type nitrogen contributes to the luminescent color, and Examples 3 to 6 and Example 8 were similarly investigated. The results are shown in Table 4.

According to Table 4, the amount of pyridine nitrogen in the cyan-based phosphor is greater than that of graphite nitrogen, and the amount of pyridine nitrogen in the white-emitting phosphor is greater than that of graphite nitrogen. In phosphors that emit orange light, the amount of pyridine nitrogen tends to be less than that of graphite nitrogen.

FIG. 16 is a diagram showing ATR-FTIR spectra of liquid samples of Examples 1, 2, and 7.

The carbon nanoparticle phosphors in the liquid samples of Examples 1, 2, and 7 were composed of C=O bonds due to amide bonds (near 1697 cm ⁻¹ ), C=C bonds due to aromatic groups (near 1530 cm ⁻¹ ), and C=C bonds due to phenols (near 1530 cm −1). It was found that it has an OH bond and a CH bond (around 1310 to 1380 cm ^-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.

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

According to FIG. 17, it was found that all the samples well absorbed light with a wavelength in the 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.

FIG. 18 is a diagram showing 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 is a diagram showing the absorption spectra of the liquid samples of Examples 5 and 6.

18 to 20 show emission spectra when each liquid sample was irradiated with an excitation wavelength of 370 nm. 19 and 20 also show the emission spectrum of Example 2 shown in FIG. 1.

It was found that the emission spectrum of Example 1 had a peak at 450 nm and emitted blue light. According to the emission spectrum of Example 7, it was found that it had a peak at 616 nm and emitted orange light. On the other hand, the emission spectrum of Example 2 showed a broad emission spectrum, unlike those of Examples 1 and 7, and had multiple wavelength components with peaks at 478 nm, 514 nm, and 612 nm. This also shows that the carbon nanoparticle phosphor in the liquid sample of Example 2 emits white light.

According to the emission spectra of Examples 3 to 6, similar to that of Example 2, it had multiple wavelength components and showed a broad emission spectrum, but due to the difference in the intensity of each wavelength component, the white color had different color rendering properties. It was shown that it emits light.

From the above, by employing the method of the present invention, it is possible to provide a carbon nanoparticle phosphor that emits blue (cyan) light, white light, or orange light by selecting the raw material components and adjusting the concentration. Further, according to the present invention, a method for synthesizing a carbon nanoparticle phosphor with excellent color rendering properties can be provided.

FIG. 21 shows a CIE chromaticity diagram plotting the luminescence of the liquid samples of Examples 1-8.

The chromaticity x and y values calculated from the emission spectra in FIGS. 18 to 20 were plotted on a CIE 1931 chromaticity diagram. FIG. 21 also shows the blackbody locus. A carbon nanoparticle phosphor whose emission color changes depending on the selection of raw materials and adjustment of concentration is provided, but surprisingly it has been found that the emission color can be changed along the blackbody locus. For example, it has been found that a white carbon nanoparticle phosphor that emits white light emits light within a deviation of ±0.01 from the black body locus (in the range of −0.01 or more and +0.01 or less) depending on the conditions.

FIG. 22 is a diagram showing two-dimensional luminescence mapping of the liquid sample of Example 1.
FIG. 23 is a diagram showing two-dimensional luminescence mapping of the liquid sample of Example 2.
FIG. 24 is a diagram showing two-dimensional luminescence mapping of the liquid sample of Example 7.

Although shown in gray scale in FIGS. 22 to 24, brighter regions indicate light emission. According to FIGS. 22 to 24, it was found that the emission wavelength of all liquid samples changed when the wavelength of the excitation light changed. The dependence of the excitation wavelength on the emission wavelength of the liquid sample of Example 7 in FIG. 24 is smaller than that of the liquid samples of Example 1 in FIG. 22 and Example 2 in FIG. This is because the liquid sample of Example 7 contains a carbon nanoparticle phosphor that emits orange light, but as shown in the absorption spectrum in Figure 17, absorption decreases when the wavelength exceeds 600 nm, making it difficult to emit light. I think so. For simplicity, the above results are summarized in Table 5.

[Example 9]
In Example 9, the powder samples of Examples 2 to 4 were used to produce a thin film-like resin molded body in which carbon nanoparticle phosphor was dispersed in polyvinylpyrrolidone (PVP, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.).

PVP powder (2 g) was added to deionized water (60 mL) and held at 90° C. for 3 hours to prepare a PVP aqueous solution (PVP concentration: 3.3% by mass). Powder samples (100 μg each) obtained in Examples 2 to 4 were added to a PVP aqueous solution (4 mL) and stirred. This was drop cast on a quartz substrate and dried at 90°C for 1 hour to obtain a thin film-like resin molded body. The content of carbon nanoparticle phosphor in the resin molded article thus obtained was 0.07% by mass. The powder samples of Examples 2 to 4 are referred to as W-CD1, W-CD2, and W-CD3, respectively, and the resulting resin molded bodies are designated as W-CD1@PVP, W-CD2@PVP, and W-CD3@PVP. It is called.

The appearance of the obtained resin molded article was observed and irradiated with a lamp that emits light with a wavelength of 365 nm. The observation results are shown in FIG. 25. The emission spectrum of the resin molded body was measured using a spectrofluorescence altimeter. CIE chromaticity (x, y) was calculated from the emission spectrum. These results are shown in FIGS. 26 and 27. These results will be summarized and explained.

FIG. 25 is a diagram showing the appearance of a resin molded article according to Example 9.

According to FIG. 25(A), it was found that the resin molded article according to Example 9 was transparent in the visible region. According to FIG. 25(B), when irradiated with an ultraviolet lamp, it was found that all of the resin molded articles according to Example 9 emitted light in a blue-white to white to warm white (white type). These emission colors were similar to those of the liquid samples of Examples 2-4.

FIG. 26 is a diagram showing the fluorescence spectrum of the resin molded article according to Example 9.

According to FIG. 26, all of the resin molded bodies according to Example 9 exhibited a broad emission spectrum, and had 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 2-4.

FIG. 27 shows a CIE chromaticity diagram plotting the luminescence of the resin molded body according to Example 9.

FIG. 27 also shows the blackbody locus. Similar to Examples 2 to 4, the white carbon nanoparticle phosphor that emits white light has a deviation of ±0.01 from the black body locus (in the range of -0.01 or more and +0.01 or less) even when combined with resin etc. as a molded product. It turned out that it emits light inside.

[Example 10]
In Example 10, a test strip in which the powder sample of Example 2 was dispersed was produced.
FIG. 28 is a diagram showing the test strip manufacturing procedure and test state.

The powder sample of Example 2 was dispersed in DMSO to prepare a phosphor dispersion (0.3% by mass, 3mg/mL). Cellulose filter paper (Whatman (registered trademark), cellulose filter) was used as the mount, and the phosphor dispersion liquid was dropped onto it at three locations in areas 1 to 3, and it was dried at 80°C to obtain a test paper. . Next, light water and heavy water were dripped into regions 1 and 3, respectively, as test solutions. Here, since water was used as the test liquid, Region 2, in which nothing was dropped, was used as a control. This was irradiated with an ultraviolet lamp and the state of luminescence was observed. The results are shown in FIG.

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

FIG. 29(A) is a diagram showing the appearance of a test paper in which a phosphor dispersion liquid is dropped onto a cellulose filter paper and carbon nanoparticle phosphors are dispersed therein. Carbon nanoparticle phosphors are contained in three locations, regions 1 to 3.

FIG. 29(B) shows how the test paper was irradiated with an ultraviolet lamp before the test liquid was dropped. According to FIG. 29(B), it can be seen that there is no change in the luminescence intensity by visual observation. FIG. 29(C) shows how the test paper after dropping the test liquid was irradiated with an ultraviolet lamp. When irradiated with an ultraviolet lamp, regions 1 and 3 where light water and heavy water were dropped, respectively, had lower luminescence intensity than region 2, which was a control. This indicates that by using the test paper of the present invention, it is possible to easily determine whether or not the test liquid contains water.

Next, water containing 0% by volume, 2.5% by volume, 5% by volume, 10% by volume, 20% by volume, and 100% by volume of heavy water was dropped on the test paper carrying the carbon nanoparticle phosphor, respectively. Emission spectra were measured using a spectrophotometer. The results are shown in FIGS. 30 and 31.

FIG. 30 is a diagram showing emission spectra for various types of water.
FIG. 31 is a diagram showing the dependence of the luminescence intensity of FIG. 30 on heavy water concentration.

FIG. 30 shows the emission spectrum when each region of the test paper was irradiated with an excitation wavelength of 370 nm. FIG. 30 also shows the emission spectrum in the control (region where no water was added). According to FIG. 30, it was found that the emission intensity at the peak near 600 nm decreased as the content of heavy water decreased, that is, as the content of light water increased.

FIG. 31 is a diagram in which the emission intensity at an emission wavelength of 600 nm is plotted against the content of heavy water. According to FIG. 31, it was found that the luminescence intensity increases linearly with the heavy water content.

Utilizing this, it is possible to detect light water (H ₂ O) contained in heavy water (D ₂ O) or to know the amount of light water (H 2 O). This can be used as a simple and inexpensive test strip to detect the amount of light water and heavy water. Furthermore, by using DMSO, DMF, acetonitrile, ethanol, etc. instead of heavy water (D ₂ O), it is also possible to know the presence and amount of light water (H ₂ O) in them.

According to the present invention, it is possible to produce a carbon nanoparticle phosphor with adjusted chromaticity by simply adjusting the raw materials, which is advantageous. Further, by using such a carbon nanoparticle phosphor, a light emitting device can be provided. In particular, a carbon nanoparticle phosphor having a specific composition is excellent as a phosphor that emits white light and exhibits high color rendering properties, so that it is possible to provide a white light emitting device such as a white LED. Furthermore, since the luminescence intensity of this material is greatly reduced by water, it is possible to provide a simple test strip that can be used to determine the amount of water in heavy water, ethanol, etc. from changes in luminescence intensity.

200 Light emitting device 210, 220 Lead wire 230 Alumina substrate 240 Violet light emitting diode element 250 Fine gold wire 260 Resin molding 270 Resin 300 Test paper 310 Inspection area 320 Mounting paper

Claims (26)

The method for producing carbon nanoparticle phosphors with controlled chromaticity is as follows:
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 method according to claim 1, 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. . 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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< If 0.3 and 0.25≦y≦0.4 are satisfied,
The organic solvent is a nitrogen-containing organic solvent,
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< If 0.44 and 0.3≦y≦0.4 are satisfied,
The organic solvent is formamide and/or N-methylformamide,
The preparing includes adding ethylenediamine (EDA), diethanolamine (DEA), urea, thiourea, ethanolamine (EA), dopamine, L-cystine, L-arginine, ethylenediaminetetraacetic acid (EDTA) to the organic solvent, and , further dissolving at least one nitrogen source selected from the group consisting of cysteamine;
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 is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. If 0.6 and 0.3≦y≦0.45 are satisfied,
the organic solvent is formamide,
3. The preparing further comprises dissolving in the organic solvent at least one nitrogen source selected from the group consisting of ammonium hydroxide, o-phenylenediamine, and p-phenylenediamine. the method of. 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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< If 0.3 and 0.25≦y≦0.4 are satisfied,
The concentration of the carbon source in the organic solvent satisfies a range of 0.05 mol/L or more and 0.2 mol/L 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 satisfies the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< If 0.44 and 0.3≦y≦0.4 are satisfied,
The concentration of the carbon source in the organic solvent satisfies a range of 0.05 mol/L or more and 0.2 mol/L or less,
The concentration of the nitrogen source in the organic solvent satisfies a 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 or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. If 0.6 and 0.3≦y≦0.45 are satisfied,
The concentration of the carbon source in the organic solvent satisfies a range of 0.05 mol/L or more and 0.2 mol/L or less,
The method according to claim 3, wherein the concentration of the nitrogen source in the organic solvent satisfies a range of 0.05 mol/L or more and 3.0 mol/L 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 satisfies the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< If 0.3 and 0.25≦y≦0.4 are satisfied,
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< If 0.44 and 0.3≦y≦0.4 are satisfied,
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 or more and 380 nm or less, the color emitted by the carbon nanoparticle phosphor is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. If 0.6 and 0.3≦y≦0.45 are satisfied,
the organic solvent is formamide,
5. A method according to claim 3 or 4, wherein the nitrogen source is ammonium hydroxide. The method according to any of claims 1 to 5, wherein the carbon source is citric acid. The method according to any one of claims 1 to 6, wherein heating the raw material solution heats the raw material solution at a temperature of 150° C. or more and 230° C. or less for a time of 5 hours or more and 15 hours or less. The method according to any one of claims 1 to 7, further comprising collecting the product produced by heating the raw material solution and heating it in vacuum. 9. The heating in vacuum is performed by heating the product at a degree of vacuum of 1 Pa or more and 10,000 Pa or less, for a time of 50° C. or more and 70° C. or less, and for a time of 30 minutes or more and 12 hours or less. Method. A carbon nanoparticle phosphor containing a carbon element, an oxygen element, a nitrogen element, and a hydrogen element,
Contains amorphous carbon and graphitic carbon,
In the carbon nanoparticle phosphor, the nitrogen element includes pyridine nitrogen, amide nitrogen, pyrrole nitrogen, and graphite nitrogen. The content of the pyridine type nitrogen is higher than that of the graphite type nitrogen,
The amorphous carbon satisfies a range of greater than 90% by volume and less than or equal to 99% by volume,
The graphitic carbon satisfies a range of 1% by volume or more and less than 10% by volume,
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 the value (x, y) on the CIE1931 chromaticity coordinates of 0.2≦x< The carbon nanoparticle phosphor according to claim 10, which satisfies 0.3 and 0.25≦y≦0.4. The amorphous carbon satisfies a range of 95% by volume or more and 99% by volume or less,
The carbon nanoparticle phosphor according to claim 11, wherein the graphitic carbon satisfies a range of 1 volume % or more and 5 volume % or less. The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.58≦p≦0.65
0.22≦q≦0.30
0.12≦r<0.16
The carbon nanoparticle phosphor according to claim 11 or 12, which satisfies the following. The contents p and q of the carbon element and nitrogen element are:
0.38<q/p≦0.41
The carbon nanoparticle phosphor according to claim 13, which satisfies the following. The content of the pyridine type nitrogen is less than that of the graphite type nitrogen,
The amorphous carbon satisfies a range of 45% by volume or more and 70% by volume or less,
The graphitic carbon satisfies a 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 satisfies the value (x, y) on the CIE1931 chromaticity coordinates of 0.3≦x< The carbon nanoparticle phosphor according to claim 10, which satisfies 0.44 and 0.3≦y≦0.4. The amorphous carbon satisfies a range of 53 volume % or more and 68 volume % or less,
The carbon nanoparticle phosphor according to claim 15, wherein the graphitic carbon satisfies a range of 32 volume % or more and 47 volume % or less. The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.57≦p≦0.65
0.20≦q<0.26
0.16≦r<0.19
The carbon nanoparticle phosphor according to claim 15 or 16, which satisfies the following. The contents p and q of the carbon element and nitrogen element are:
0.32<q/p<0.44
The carbon nanoparticle phosphor according to claim 17, which satisfies the following. The content of the pyridine type nitrogen is less than that of the graphite type nitrogen,
The amorphous carbon satisfies a range of 60 volume % or more and 90 volume % or less,
The graphitic carbon satisfies a range of 10% by volume or more and 40% 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 is 0.44≦x≦ as the (x, y) value on the CIE1931 chromaticity coordinates. The carbon nanoparticle phosphor according to claim 10, which satisfies 0.6 and 0.3≦y≦0.45. The amorphous carbon satisfies a range of 60 volume % or more and 83 volume % or less,
The carbon nanoparticle phosphor according to claim 19, wherein the graphitic carbon satisfies a range of 17% by volume or more and 40% by volume or less. The content p (atomic %) of the carbon element, the content q (atomic %) of the nitrogen element, and the content r (atomic %) of the oxygen element (where p+q+r=1) are respectively,
0.58≦p≦0.65
0.15≦q≦0.21
0.19≦r≦0.21
The carbon nanoparticle phosphor according to claim 19 or 20, which satisfies the following. The contents p and q of the carbon element and nitrogen element are:
0.25<q/p<0.34
The carbon nanoparticle phosphor according to claim 21, which satisfies the following. The carbon nanoparticle phosphor according to any one of claims 10 to 22, wherein the carbon nanoparticle phosphor has a diameter in a range of 1 nm or more and 20 nm or less. 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 10 to 23. 25. The light emitting device according to claim 24, wherein the phosphor is a resin molded body in which the carbon nanoparticle phosphor is dispersed. A test paper for determining whether a test liquid contains water,
The test paper contains the carbon nanoparticle phosphor according to any one of claims 10 to 23.