Luminescent nanocarbon
By optimizing the weight average molecular weight and production method of luminescent nanocarbons, their light resistance is significantly enhanced, addressing the issue of insufficient light resistance in existing luminescent nanocarbons.
Patent Information
- Application Number
- JP2023206775
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-12-07
- Publication Date
- 2025-06-19
AI Technical Summary
Luminescent nanocarbons with luminescence mechanisms based on dye structures often have insufficient light resistance, necessitating an improvement in this aspect.
The weight average molecular weight of luminescent nanocarbons, measured by size exclusion chromatography using a UV detector with polystyrene as a standard, is optimized to be between 1,000 and 100,000, and these nanocarbons are produced through heat-synthesis of carbon and nitrogen source compounds in an open system.
This approach results in luminescent nanocarbons with enhanced light resistance, as the encapsulation of organic dyes within the particles reduces their exposure to oxygen, thereby improving stability.
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Abstract
Description
Technical Field
[0001] The present invention relates to luminescent nanocarbon, a resin composition containing the luminescent nanocarbon, and a method for producing the luminescent nanocarbon.
Background Art
[0002] Quantum dots are those in which 10 to 1000 atoms form fine particles having a diameter of about 2 to 20 nm. Since the fine particles do not affect each other, and the electrons that bind the atoms forming one fine particle are confined within a space of at most 20 nm, they exhibit properties different from those of general substances having the same composition. For example, when quantum dots are irradiated with ultraviolet light, it is known that they emit fluorescence with a wide range of emission wavelengths from near ultraviolet to near infrared depending on the properties of the atoms forming the quantum dots and the size of the fine particles. However, generally well-known metal-based quantum dots use harmful metals such as highly toxic cadmium, selenium, and lead, and rare metals such as europium and terbium. Therefore, there is a demand for the development of quantum dots that can reduce the environmental load and use inexpensive and simple materials. As such quantum dots, carbon quantum dots in which the atoms are carbon have been studied.
[0003] Carbon quantum dots are also referred to as luminescent nanocarbon, and as its luminescence mechanism, there are (1) luminescence due to π-conjugation of a graphene core, (2) luminescence derived from surface defects of the luminescent nanocarbon, and (3) luminescence due to a specific dye structure. For example, in Non-Patent Document 1, a method of heating a carbon source compound and a nitrogen source compound to synthesize luminescent nanocarbons is disclosed, and in Non-Patent Document 2, a solvothermal method of synthesizing luminescent nanocarbons by heating above the boiling point of a solvent using a pressure-resistant sealed container such as an autoclave is disclosed. However, according to Non-Patent Documents 3 and 4, it has been shown that the luminescent nanocarbons obtained by the synthesis methods disclosed in Non-Patent Documents 1 and 2 often have a luminescence mechanism based on a specific dye structure. And Non-Patent Document 5 discloses that various stabilities of luminescent nanocarbons have been studied.
Prior Art Documents
Non-Patent Documents
[0004]
Non-Patent Document 1
Non-Patent Document 2
Non-Patent Document 3
Non-Patent Document 4
Non-Patent Document 5
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, in the luminescence due to the dye structure, the light resistance is not sufficient, and an improvement in the light resistance of luminescent nanocarbons is required. An object of the present invention is to provide a luminescent nanocarbon having excellent light resistance, a resin composition containing the luminescent nanocarbon, and a method for producing the luminescent nanocarbon.
Means for Solving the Problems
[0006] The present inventors have found that the above problems can be solved by the weight average molecular weight measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance for the luminescent nanocarbon being in a specific range. That is, the present invention relates to the following [1] to [3]. [1] A luminescent nanocarbon having a weight average molecular weight of 1,000 or more and 100,000 or less, measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance. [2] A resin composition containing the luminescent nanocarbon according to [1] and a resin, wherein the resin is at least one selected from the group consisting of an acrylic resin, a carbonate resin, an olefin resin, a vinyl chloride resin, an ethylene vinyl acetate resin, a vinyl acetate resin, a vinyl alcohol resin, and a polyester resin. [3] A method for producing a luminescent nanocarbon, comprising a step of heat-synthesizing a carbon source compound (C) and a nitrogen source compound (N) in an open system at 100°C or higher and 350°C or lower to obtain the luminescent nanocarbon, wherein the weight average molecular weight of the luminescent nanocarbon obtained by this step, measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance, is 1,000 or more and 100,000 or less.
Effects of the Invention
[0007] According to the present invention, it is possible to provide a luminescent nanocarbon having excellent light resistance, a resin composition containing the luminescent nanocarbon, and a method for producing the luminescent nanocarbon.
Brief Description of the Drawings
[0008]
Figure 1
Mode for Carrying Out the Invention
[0009] [Luminescent Nanocarbon] The luminescent nanocarbon of the present invention (hereinafter, also simply referred to as "luminescent nanocarbon") has a weight average molecular weight of 1,000 or more and 100,000 or less as measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance.
[0010] According to the present invention, the luminescent nanocarbon has excellent light resistance. The reason is not clear, but it is considered as follows. Generally, when light hits under conditions where an organic dye is in contact with oxygen, it is known that the generated radicals become oxy radicals, and the decomposition of the structure is promoted. Therefore, when the luminescence mechanism of the luminescent nanocarbon is luminescence due to the structure of the organic dye, it is important to inhibit the contact between the organic dye and oxygen. The particle size of the luminescent nanocarbon can be measured by a transmission electron microscope (TEM) or an atomic force microscope (AFM), but it is unclear whether the object being observed has light absorption. For example, in a transmission electron microscope (TEM) or an atomic force microscope (AFM), although the object being observed has the shape of particles, it may consist only of by-products that do not contain an organic dye. In the present invention, the weight average molecular weight of the luminescent nanocarbon is measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance. In the size exclusion chromatography (SEC) in the present invention, since detection is performed by UV absorption using a UV detector, it is clear that the luminescent nanocarbon absorbs UV light at its molecular weight, and the weight average molecular weight measured by such a method can be used as an index of the size of the luminescent nanocarbon containing an organic dye. In the present invention, when the weight-average molecular weight of the luminescent nanocarbon measured by the above size-exclusion chromatography is equal to or greater than a specific value, the organic dye is incorporated into the particles of the luminescent nanocarbon rather than being in a free state outside the particles of the luminescent nanocarbon. Also, since the size of the particles of the luminescent nanocarbon is large, it is considered that the contact between the organic dye encapsulated in the particles of the luminescent nanocarbon and oxygen is less likely to occur, and the light resistance can be improved.
[0011] From the viewpoint of improving the light resistance, the weight-average molecular weight of the luminescent nanocarbon of the present invention measured by size-exclusion chromatography using a UV detector with polystyrene as a standard substance is preferably 1,000 or more, more preferably 3,000 or more, still more preferably 5,000 or more, even more preferably 8,000 or more, even more preferably 10,000 or more, and even more preferably 15,000 or more. And from the viewpoint of reducing adjacent organic dyes, suppressing concentration quenching, and improving the quantum yield, it is preferably 100,000 or less, more preferably 80,000 or less, still more preferably 50,000 or less, and even more preferably 30,000 or less. In the chromatogram of the molecular weight distribution of the luminescent nanocarbon of the present invention measured by size-exclusion chromatography using a UV detector with polystyrene as a standard substance, the ratio of the area corresponding to the component with a molecular weight of 1,000 or more to the total area is preferably 30% or more, more preferably 40% or more, still more preferably 50% or more from the viewpoint of improving the light resistance. And from the viewpoint of reducing adjacent organic dyes, suppressing concentration quenching, and improving the quantum yield, it is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less.
[0012] The wavelength absorbed by the luminescent nanocarbon of the present invention is preferably 100 nm or more, more preferably 150 nm or more, still more preferably 200 nm or more, even more preferably 280 nm or more, from the viewpoint of the availability of the luminescent nanocarbon, and, from the same viewpoint as above, preferably 435 nm or less, more preferably 400 nm or less, still more preferably 380 nm or less. The wavelength at which the luminescent nanocarbon of the present invention emits light when it absorbs light with a wavelength of 340 nm is preferably 350 nm or more, more preferably 360 nm or more, still more preferably 370 nm or more, even more preferably 380 nm or more, from the viewpoint of the availability of the luminescent nanocarbon, and, from the same viewpoint as above, preferably 600 nm or less, more preferably 550 nm or less, still more preferably 530 nm or less, even more preferably 500 nm or less. The peak top of the emission wavelength of the luminescent nanocarbon of the present invention is preferably 380 nm or more, more preferably 390 nm or more, still more preferably 400 nm or more, from the viewpoint of the availability of the luminescent nanocarbon, and, from the same viewpoint as above, preferably 500 nm or less, more preferably 490 nm or less, still more preferably 450 nm or less.
[0013] The quantum yield (QY) of the luminescent nanocarbon of the present invention is preferably 10% or more, more preferably 20% or more, still more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, from the viewpoint of improving the luminescence characteristics of the luminescent nanocarbon, and the upper limit is 100% or less. The absorbance (A) per solid content of the luminescent nanocarbon is preferably 3,000 or more, more preferably 5,000 or more, still more preferably 7,000 or more, from the viewpoint of improving the luminescence characteristics of the luminescent nanocarbon, and, from the viewpoint of the ease of manufacturing the luminescent nanocarbon, preferably 10,000 or less. The value obtained by multiplying the quantum yield (QY) by the absorbance (A) per solid content of the luminescent nanocarbon [(QY)×(A)] is preferably 300 or more, more preferably 1,000 or more, still more preferably 2,000 or more, even more preferably 3,000 or more, even more preferably 4,000 or more, from the viewpoint of improving the luminescence characteristics of the luminescent nanocarbon, and is preferably 9,000 or less from the viewpoint of ease of production of the luminescent nanocarbon.
[0014] The weight average molecular weight of the luminescent nanocarbon of the present invention, the ratio of the area corresponding to the component having a molecular weight of 1,000 or more in the chromatogram of the molecular weight distribution, the absorption wavelength, the emission wavelength, the absorbance (A) per solid content of the luminescent nanocarbon, and the quantum yield (QY) are measured or calculated by the methods described in the examples, but measurement values or calculated values obtained using devices other than the devices described in the examples may be adopted as long as the measurement principle is the same as the method described in the examples.
[0015] From the viewpoint of improving the light resistance, the luminescent nanocarbon of the present invention is preferably a heat synthesis product of a carbon source compound (C) and a nitrogen source compound (N). In the present invention, the weight average molecular weight of the luminescent nanocarbon, the ratio of the area corresponding to the component having a molecular weight of 1,000 or more in the chromatogram of the molecular weight distribution, the absorption wavelength, the absorbance (A) per solid content of the luminescent nanocarbon, and the quantum yield (QY) can be appropriately adjusted by the types and the amount ratios of the carbon source compound (C) and the nitrogen source compound (N), and the production conditions such as the temperature or time of the heat synthesis.
[0016] (Carbon source compound (C)) Examples of the carbon source compound (C) include organic acids; sugars (glucose); polyvinyl alcohol; and ninhydrin. Examples of the organic acid include aliphatic polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, and itaconic acid; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, and trimellitic acid; and hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, galactaric acid, quinic acid, glyceric acid, gluconic acid, glucuronic acid, ascorbic acid, and gallic acid. Among these, from the viewpoint of improving light resistance, the carbon source compound (C) is preferably an organic acid, more preferably at least one selected from the group consisting of aliphatic polycarboxylic acids, aromatic polycarboxylic acids, and hydroxy acids, still more preferably a hydroxy acid, and even more preferably at least one selected from the group consisting of citric acid, malic acid, tartaric acid, galactaric acid, quinic acid, glyceric acid, gluconic acid, glucuronic acid, ascorbic acid, and gallic acid, and even more preferably citric acid.
[0017] (Nitrogen source compound (N)) Examples of the nitrogen source compound (N) preferably include amine compounds such as hydroxyamine, alkoxyamine, aliphatic amine, aromatic amine, polyamine, and heterocyclic amine. Examples of the hydroxyamine include monomethanolamine, dimethanolamine, trimethanolamine, monoethanolamine, diethanolamine, triethanolamine, 2-(2-aminoethoxy)ethanol, and tris(hydroxymethyl)aminomethane. An example of the alkoxyamine is 3-butoxypropylamine. Examples of the aliphatic amine include monoamines such as hexylamine, N,N-dimethylethylenediamine, and oleylamine; and diamines such as ethylenediamine. An example of the aromatic amine is phenylenediamine. Among these, the nitrogen source compound (N) is preferably an amine compound from the viewpoint of improving light resistance, more preferably at least one selected from the group consisting of hydroxyamine and aliphatic amine, still more preferably at least one selected from the group consisting of tris(hydroxymethyl)aminomethane, monoethanolamine, and ethylenediamine, and even more preferably tris(hydroxymethyl)aminomethane.
[0018] The luminescent nanocarbon of the present invention preferably contains a structural unit derived from citric acid as the carbon source compound (C) and a structural unit derived from tris(hydroxymethyl)aminomethane as the nitrogen source compound (N). When the luminescent nanocarbon contains a structural unit derived from citric acid and a structural unit derived from tris(hydroxymethyl)aminomethane, the structures of citric acid and tris(hydroxymethyl)aminomethane remain in the structure of the luminescent nanocarbon and act as modifying groups for the graphene structure, thereby affecting its π-electron conjugation orbit and improving light resistance.
[0019] [Method for producing luminescent nanocarbon] From the viewpoint of improving light resistance, the luminescent nanocarbon of the present invention is preferably produced by a method including a step of heat-synthesizing a carbon source compound (C) and a nitrogen source compound (N) to obtain luminescent nanocarbon (hereinafter, also referred to as "Step I"). That is, the method for producing the luminescent nanocarbon of the present invention includes a step of heat-synthesizing a carbon source compound (C) and a nitrogen source compound (N) to obtain luminescent nanocarbon, and the weight average molecular weight of the luminescent nanocarbon obtained by Step I, measured by size exclusion chromatography using polystyrene as a standard substance with a UV detector, is 1,000 or more and 100,000 or less.
[0020] The preferred carbon source compound (C) and nitrogen source compound (N) used in Step I are as described above. In Step I, from the viewpoints of improving the quantum yield and improving the light resistance of the resulting luminescent nanocarbon, the molar ratio of the amount of the carbon source compound (C) to the total charged amount of the carbon source compound (C) and the nitrogen source compound (N) [carbon source compound (C) / (carbon source compound (C) + nitrogen source compound (N))] (hereinafter referred to as "molar ratio [carbon source compound (C) / (carbon source compound (C) + nitrogen source compound (N))]") is preferably 0.2 or more, more preferably 0.3 or more, still more preferably 0.4 or more, even more preferably 0.45 or more, and from the same viewpoints as above, preferably 0.65 or less, more preferably 0.6 or less, still more preferably 0.55 or less.
[0021] From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the thermal synthesis in Step I is preferably carried out by stirring with a commonly used mixer while heating the carbon source compound (C) and the nitrogen source compound (N) under conditions where water or an organic solvent is substantially absent in the reaction system, that is, under solvent-free conditions. Also, from the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the thermal synthesis in Step I is preferably carried out in an open system. In the present invention, the "open system" means a reaction system in which the inside of the reaction vessel is not sealed and a liquid such as water volatilizes and is released outside the reaction system.
[0022] From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the temperature of the thermal synthesis in Step 1 is preferably 100°C or higher, more preferably 110°C or higher, still more preferably 120°C or higher, even more preferably 130°C or higher, and preferably 350°C or lower, more preferably 300°C or lower, still more preferably 250°C or lower, even more preferably 200°C or lower. From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the heating synthesis time in Step 1 is preferably 0.5 hours or more, more preferably 1 hour or more, still more preferably 2 hours or more, and from the viewpoint of production efficiency, preferably 200 hours or less, more preferably 100 hours or less, still more preferably 50 hours or less, even more preferably 30 hours or less, even more preferably 20 hours or less, and even more preferably 10 hours or less.
[0023] From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the heating synthesis in Step I is preferably multi-step heating synthesis, more preferably two-step heating synthesis. In the case of two-step heating synthesis, it is preferable to change the temperature between the first heating synthesis and the second heating synthesis, and it is more preferable to carry out the second heating synthesis at a temperature higher than the temperature of the second heating synthesis. After carrying out the first heating synthesis at 100°C or more and 150°C or less, it is still more preferable to carry out the second heating synthesis at more than 150°C and 350°C or less. From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the temperature of the first heating synthesis is preferably 100°C or more, more preferably 110°C or more, still more preferably 120°C or more, even more preferably 130°C or more, and preferably 150°C or less, more preferably 145°C or less, still more preferably 140°C or less. From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the time of the first heating synthesis is preferably 0.5 hours or more, more preferably 1 hour or more, and from the viewpoint of production efficiency, preferably 50 hours or less, more preferably 30 hours or less, still more preferably 10 hours or less, even more preferably 5 hours or less, and even more preferably 3 hours or less.
[0024] From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the temperature of the second heating synthesis is preferably more than 150°C, more preferably 160°C or more, still more preferably 170°C or more, and preferably 350°C or less, more preferably 300°C or less, still more preferably 250°C or less, and even more preferably 200°C or less. From the viewpoint of improving the light resistance of the resulting luminescent nanocarbon, the time for the second heat synthesis is preferably 0.5 hours or more, more preferably 1 hour or more, and from the viewpoint of production efficiency, it is preferably 200 hours or less, more preferably 100 hours or less, still more preferably 50 hours or less, even more preferably 30 hours or less, and even more preferably 20 hours or less.
[0025] The luminescent nanocarbon of the present invention has a particle diameter of 1 nm or more and 20 nm or less as observed by an electron microscope. Therefore, the luminescent nanocarbon of the present invention can be widely used in various fields of electricity, chemistry, and biology, such as the fields of pollutant diagnosis, measurement, and removal, bio (molecule and cell) imaging, sensing, labeling, and gene expression research reagents, DDS (Drug Delivery System) fields, and quantum dot solar cell fields for solar energy conversion.
[0026] [Resin composition] The resin composition of the present invention contains luminescent nanocarbon and a resin. As the resin, one or more selected from the group consisting of acrylic resins, carbonate resins, olefin resins, vinyl chloride resins, ethylene vinyl acetate resins, vinyl acetate resins, vinyl alcohol resins, and polyester resins are preferably mentioned. When the resin composition of the present invention is used for applications such as displays, lighting fixtures, and signboards, from the viewpoints of transparency, impact resistance, and durability, one or more selected from the group consisting of acrylic resins and carbonate resins are more preferable, acrylic resins are still more preferable, (meth)acrylic acid ester polymers are even more preferable, and methyl methacrylate polymers are even more preferable. Here, "(meth)acrylic acid ester" means acrylic acid ester or methacrylic acid ester. Also, when the resin composition of the present invention is used for agricultural films, from the viewpoints of cost, processability, and durability, one or more selected from the group consisting of olefin resins, vinyl chloride resins, and vinyl acetate resins are more preferable. When the resin composition of the present invention is used as a sealing material for a solar panel, an ethylene vinyl acetate-based resin is more preferable from the viewpoints of light transmittance and durability. When the resin composition of the present invention is used for applications such as a polarizing film and a packaging material, a vinyl alcohol-based resin is more preferable from the viewpoints of water solubility, film-forming property, and oxygen barrier property.
[0027] The content of the luminescent nanocarbon in the resin composition of the present invention is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 1 part by mass or more, and even more preferably 3 part by mass or more with respect to 100 parts by mass of the resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and still more preferably 6 parts by mass or less.
[0028] The resin composition of the present invention is preferably used as a film, for example, by preparing a coating solution containing a luminescent nanocarbon, the resin, and a solvent, and heating the obtained coating solution at an appropriate temperature to remove the solvent. Examples of the solvent used for preparing the coating solution include dimethylformamide, acetone, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, and dimethyl sulfoxide. The concentration of the coating solution can be appropriately adjusted according to the use and handleability of the resin composition of the present invention.
Examples
[0029] In the following production examples, examples, and comparative examples, "parts" means "parts by mass" unless otherwise specified. The measurement methods or calculation methods for each physical property, etc. are as follows.
[0030] (1) Measurement of solid content concentration Weighed 10.0 g of sodium sulfate, which had been equilibrated in a desiccator, into a 30 mL polypropylene container (φ: 40 mm, height: 30 mm). Added approximately 1.0 g of the sample thereto, mixed them, then weighed accurately. Maintained at 105 °C for 2 hours to remove volatile components, and left it in the desiccator for 15 minutes, then measured the mass. The mass of the sample after removing volatile components was taken as the solid content, and divided by the mass of the added sample to obtain the solid content concentration (mass %).
[0031] (2) Measurement of weight-average molecular weight (Mw) The weight-average molecular weight (Mw) was determined by size exclusion chromatography (SEC). The measurement conditions are shown below. GPC apparatus: "HLC-8320GPC" manufactured by Tosoh Corporation Columns: "TSKgel SuperAWM-H", "TSKgel SuperAW3000", "TSKgel guardcolumn Super AW-H" manufactured by Tosoh Corporation Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 43 mmol / L, respectively Flow rate: 0.5 mL / min Standard substance: Monodisperse polystyrene kits with known molecular weights "PStQuick B (F-550, F-80, F-10, F-1, A-1000)", "PStQuick C (F-288, F-40, F-4, A-5000, A-500)" (all manufactured by Tosoh Corporation) Detector: UV detector Wavelength: 340 nm Measurement sample: 0.5 g of luminescent nanocarbon was mixed with 10 mL of the above eluent in a glass vial, stirred with a magnetic stirrer at 25 °C for 10 hours, and filtered with a syringe filter ("DISMIC-13HP" manufactured by Advantec Co., Ltd., membrane filter material: PTFE, pore size: 0.2 μm) was used.
[0032] (3) Measurement of absorption spectrum and absorbance, and calculation of absorbance (A) per solid content The absorption spectrum and absorbance were measured under the following conditions. Apparatus: Spectrophotometer ("U-3900" manufactured by Hitachi, Ltd.) Measurement environment: Normal temperature and pressure Measurement wavelength: 300 nm to 800 nm Measurement concentration: Concentration (mass %) at which the absorbance at 340 nm is 0.03 to 0.09 Measurement sample: 1 g of luminescent nanocarbon was mixed with 10 mL of ion-exchanged water in a glass vial, stirred with a magnetic stirrer at 90 °C for 5 hours, cooled, and then filtered through a syringe filter ("DISMIC-13HP" manufactured by Advantec Co., Ltd., membrane filter material: PTFE, pore size: 0.2 μm), and the solid content concentration was measured by the method described in (1) above. Subsequently, it was diluted with ion-exchanged water to have an absorbance at the above-measured concentration, and used as the measurement sample. The measurement concentration was calculated based on the dilution ratio. The absorbance (A) per solid content of the luminescent nanocarbon was calculated from the following formula. Absorbance (A) per solid content of the luminescent nanocarbon = [Absorbance at 340 nm / (Measurement concentration (mass %) / 100)]
[0033] (4) Measurement of emission spectrum The emission spectrum was measured under the following conditions. Apparatus: Fluorescence spectrophotometer ("Fluorolog-3" manufactured by Horiba, Ltd.) Measurement environment: Normal temperature and pressure Excitation light source: Xe lamp ("FL-1039A" manufactured by Horiba, Ltd.) Spectrometer: iHR320 (manufactured by Horiba, Ltd., product name) Measurement method: Emission was detected at an angle of 90 degrees with respect to the excitation light source. Excitation wavelength: 340 nm Measurement wavelength: 345 nm to 650 nm Measurement concentration: Concentration at which the absorbance at 340 nm is 0.03 to 0.09 Measurement sample: The sample adjusted for the above absorbance measurement was used.
[0034] (5) Calculation of quantum yield (QY) For a dye molecular solution containing quinidine sulfate (the quantum yield in a 0.1 mol sulfuric acid aqueous solution is 54%) whose quantum yield is known as standard data and an aqueous dispersion of luminescent nanocarbon, the following values were measured and calculated from the following formula. Absorbance A: Absorbance at 340 nm in the absorption spectrum Emission intensity I: Integrated value of the emission intensity from 345 nm to 650 nm Quantum yield (QY) = Quantum yield (QY) of quinidine × (Emission intensity I of luminescent nanocarbon / Absorbance A of luminescent nanocarbon) / (Emission intensity I of quinidine / Absorbance A of quinidine)
[0035] Example 1 58.30 parts of citric acid as the carbon source compound (C) and 36.60 parts of tris(hydroxymethyl)aminomethane as the nitrogen source compound (N) were added to a 1000 mL separable flask with a three-necked lid, and the separable flask was immersed in an oil bath. While stirring at 50 rpm with a stirring blade, the temperature of the oil bath was raised to 140 °C. The powder in the separable flask melted from about 130 °C and became liquid at 140 °C. Heating and stirring were carried out in an open system for 1.0 hour while maintaining the temperature at 140 °C. Then, the temperature of the oil bath was raised to 180 °C, and heating and stirring were carried out in an open system for 1.0 hour while maintaining the temperature at 180 °C. The solution in the separable flask became an orange cream-like viscous substance. Then, the separable flask was taken out of the oil bath, cooled to room temperature, and the obtained solid was ground in a mortar to obtain orange powder of luminescent nanocarbon (CD1). Various physical properties, etc. of the obtained luminescent nanocarbon (CD1) were measured or calculated by the aforementioned method. The results are shown in Table 1. Also, the absorption spectrum and emission spectrum of the obtained luminescent nanocarbon (CD1) are shown in Figure 1.
[0036] Examples 2 to 7 and Comparative Examples 4 to 7 In Example 1, the heating temperature, heating time, molar ratio [carbon source compound (C) / (carbon source compound (C)+nitrogen source compound (N))], and type of carbon source compound (C) or nitrogen source compound (N) were changed as shown in Table 1, and the same procedure as in Example 1 was repeated to obtain luminescent nanocarbons (CD2) to (CD7) and (C-CD4) to (C-CD7), respectively.
[0037] Comparative Example 1 To a No. 8 vial, 0.68 parts of citric acid as a carbon source compound (C), 0.43 parts of trishydroxymethylaminomethane as a nitrogen source compound (N), and 3.90 parts of ion-exchanged water were added and dissolved, and then heated in an open system using a household microwave oven (manufactured by Panasonic Corporation, product number: NE-FL100-W) at 600 W for 60 seconds to obtain a luminescent nanocarbon (C-CD1) in the form of an orange foam.
[0038] Comparative Example 2 10.00 parts of ion-exchanged water was added to 1.75 parts of citric acid as a carbon source compound (C) and 1.10 parts of trishydroxymethylaminomethane as a nitrogen source compound (N), and dissolved at room temperature. The obtained aqueous solution was added to a portable reactor (manufactured by Taiatsu Glass Industry Co., Ltd., product number: TVS-1-30 without inner cylinder) and placed in an oil bath. The temperature was raised to 180°C while stirring with a magnetic stirrer, and the reaction was carried out for 8 hours while maintaining the temperature at 180°C. Thereafter, the reaction vessel was air-cooled, the orange aqueous solution was taken out, and dried at 40°C for 48 hours to obtain an orange luminescent nanocarbon (C-CD2).
[0039] Comparative Example 3 To 1.75 parts of citric acid as the carbon source compound (C) and 1.10 parts of tris(hydroxymethyl)aminomethane as the nitrogen source compound (N), 10.00 parts of 2-propanol was added and dissolved at room temperature. The resulting aqueous solution was added to a portable reactor (manufactured by Pressure Glass Industry Co., Ltd., product number: TVS-1-30, without inner cylinder) and placed in an oil bath. While stirring with a magnetic stirrer, the temperature was raised to 180 °C and the reaction was carried out for 8 hours while maintaining the temperature at 180 °C. Then, the reaction vessel was air-cooled, and the orange aqueous solution was taken out and dried at 40 °C for 48 hours to obtain orange-emitting nanocarbon (C-CD3).
[0040] Using the luminescent nanocarbons obtained in the examples and comparative examples, the following light resistance evaluation was carried out. The results are shown in Table 1.
[0041] [Evaluation of Light Resistance] (Preparation of Test Film) 1 part of each luminescent nanocarbon obtained in the examples and comparative examples, 20 parts of methyl methacrylate polymer (manufactured by Fujifilm Wako Pure Chemical Corporation, product code: 138-02735), and 79 parts of dimethylformamide were mixed and stirred at room temperature for 24 hours to prepare a coating solution. The obtained coating solution was applied to a corona-discharge-treated PET film (manufactured by Futamura Chemical Co., Ltd., product number: FE2001, film thickness: 20 μm) using a bar coater (No. 8) and dried at 80 °C for 20 minutes to obtain a test film. (Light Resistance Test) Using the obtained test film, a light resistance test was carried out under the following conditions. Equipment used: Xenon weather meter tester (「Ci3000」manufactured by ATLAS) Light source used: Xenon lamp Illuminance: 50 W / cm 2 (300 nm - 400 nm) Test time: 0.5 hour Temperature: 38 °C Humidity: 50%RH condition (Calculation of Absorbance Retention Rate) For the test film before the test and the test film after the test, absorbance was measured under the following conditions, the absorbance retention rate was calculated from the following formula, and the light resistance was evaluated. Apparatus: Spectrophotometer ("U-3900" manufactured by Hitachi, Ltd.) Measurement environment: Normal temperature and pressure Measurement wavelength: 300 nm to 800 nm Measurement sample: Test film before the test and test film after the test Absorbance retention rate (%) = (Absorbance at 340 nm of the film after the test / Absorbance at 340 nm of the film before the test) × 100
[0042]
Table 1
[0043] It can be seen from Table 1 that the luminescent nanocarbon of the example is superior in light resistance compared to the comparative example.
Industrial applicability
[0044] According to the present invention, a luminescent nanocarbon excellent in light resistance can be provided, and such a luminescent nanocarbon can be suitably used in various fields of electricity, chemistry, and biology, such as the fields of pollutant diagnosis, measurement, and removal, bio (molecule and cell) imaging, sensing, labeling, and gene expression research reagents, DDS (Drug Delivery System), and quantum dot solar cells for solar energy conversion.
Claims
1. A luminescent nanocarbon having a weight average molecular weight of 1,000 or more and 100,000 or less, measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance.
2. The luminescent nanocarbon according to claim 1, wherein in the chromatogram of the molecular weight distribution measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance, the ratio of the area corresponding to the component having a molecular weight of 1,000 or more is 30% or more with respect to the total area.
3. The luminescent nanocarbon according to claim 1 or 2, having a quantum yield (QY) of 40% or more and 100% or less.
4. The luminescent nanocarbon according to any one of claims 1 to 3, wherein the peak top of the emission wavelength is 380 nm or more and 500 nm or less.
5. A resin composition containing the luminescent nanocarbon according to any one of claims 1 to 4 and a resin, wherein the resin is at least one selected from the group consisting of an acrylic resin, a carbonate resin, an olefin resin, a vinyl chloride resin, an ethylene vinyl acetate resin, a vinyl acetate resin, a vinyl alcohol resin, and a polyester resin.
6. A step of heating and synthesizing a carbon source compound (C) and a nitrogen source compound (N) in an open system at 100°C or more and 350°C or less to obtain a luminescent nanocarbon, A method for producing a luminescent nanocarbon, wherein the weight average molecular weight of the luminescent nanocarbon obtained by this step, measured by size exclusion chromatography using a UV detector with polystyrene as a standard substance, is 1,000 or more and 100,000 or less.
7. The production method of the luminescent nanocarbon according to claim 6, wherein the molar ratio of the charged amount of the carbon source compound (C) to the total charged amount of the carbon source compound (C) and the nitrogen source compound (N) [carbon source compound (C) / (carbon source compound (C) + nitrogen source compound (N))] is 0.2 or more and 0.65 or less.
8. The production method of the luminescent nanocarbon according to claim 6 or 7, wherein the carbon source compound (C) is an organic acid.
9. The production method of the luminescent nanocarbon according to any one of claims 6 to 8, wherein the carbon source compound (C) is citric acid.
10. The production method of the luminescent nanocarbon according to any one of claims 6 to 9, wherein the nitrogen source compound (N) is at least one selected from the group consisting of hydroxyamine and aliphatic amine.
11. The production method of the luminescent nanocarbon according to any one of claims 6 to 10, wherein the nitrogen source compound (N) is tris(hydroxymethyl)aminomethane.
12. The production method of the luminescent nanocarbon according to any one of claims 6 to 11, wherein the thermal synthesis is carried out in an open system at 130°C or higher and 350°C or lower for 0.5 hours or more and 200 hours or less.
13. The production method of the luminescent nanocarbon according to any one of claims 6 to 11, wherein the thermal synthesis is a two-step thermal synthesis. After the first thermal synthesis is carried out at 120°C or higher and 150°C or lower, the second thermal synthesis is carried out at higher than 150°C and 350°C or lower.
14. The production method of the luminescent nanocarbon according to claim 13, wherein the time of the second thermal synthesis is 0.5 hours or more and 200 hours or less.
15. The production method of the luminescent nanocarbon according to any one of claims 6 to 14, wherein the thermal synthesis is carried out without a solvent.