Colorful fluorescent powder as well as spray drying preparation method and application thereof

Abstract

The invention belongs to the field of fluorescent materials. The invention provides a spray drying preparation method of colorful fluorescent powder. The spray drying preparation method comprises the following steps: (1) preparing colorful carbon quantum dots; (2) preparing a colorful carbon quantum dot solution; (3) dialyzing the colorful carbon quantum dot solution in the step (2) by using a dialysis bag, or mixing the colorful carbon quantum dot solution with a carrier solution to obtain a mixed solution; and (4) preparing the colorful fluorescent powder: setting parameters of a spray drying device, sucking the mixed solution in the step (3) into the spray drying device at a constant speed through a rubber tube under magnetic stirring for spray drying, and collecting a solid powder product which is the colorful fluorescent powder. The invention also provides the colorful fluorescent powder. The invention also provides application of the colorful fluorescent powder. The colorful fluorescent powder is used for preparing display devices, laser illumination, LED illumination or noctilucent materials. The preparation and synthesis method of the fluorescent powder is simple, the reaction repeatability is high, and production can be expanded.

Description

Technical Field

[0001] The invention relates to the field of fluorescent materials, and in particular to a multi-colored fluorescent powder and a spray drying preparation method and application thereof. Background Art

[0002] In the field of LED (light-emitting diode) lighting, colorful phosphors are used to convert blue light or other monochromatic light emitted by LED chips. By combining with different phosphors, white light or various colored lights can be obtained. They are widely used in home lighting, commercial lighting, backlight sources and other fields.

[0003] Existing methods for preparing colorful phosphors include high-temperature solid-phase reaction method, sol-gel method, coprecipitation method, microwave synthesis method, etc. Among them, the high-temperature solid-phase reaction method is to mix the matrix material and activator and other raw materials in proportion, make the mixture uniform by ball milling, and then calcine at high temperature to promote the solid-state reaction of the raw materials to generate phosphors. However, the product particle size of this method is large, and subsequent grinding treatment may be required to improve the luminescence performance and application performance. The operation is cumbersome, and local overheating is prone to occur at high temperature, affecting the uniformity of the reaction; the sol-gel method dissolves metal alkoxides or inorganic salts in a solvent to form a precursor solution, which is hydrolyzed and polymerized to form a sol. After drying and heat treatment, it is converted into fluorescent powder. However, this method is easy to form lumps during the drying process, and an additional grinding step is required to obtain powder of the required particle size, and the whole process is time-consuming. The co-precipitation method is to mix metal salt solutions in a certain proportion, add a precipitant, and control the pH value and reaction conditions to allow metal ions to co-precipitate to form a precursor, which is then heat treated to obtain the fluorescent powder. This method obtains particles that are not very uniform in shape and size, and requires more subsequent treatments such as grinding and screening to optimize performance, and more treatments are required to prevent or reduce agglomeration. The subsequent treatment is cumbersome and is not suitable for large-scale industrial production needs.

[0004] In addition, the Chinese patent CN202010499499.0 applied by the inventor discloses a microwave preparation method for colorful phosphors, which comprises preparing a fluorescent substance into an aqueous solution or ethanol solution of a certain concentration; preparing salt into a saturated salt solution, adding a certain amount of polyethylene glycol to the saturated salt solution and stirring evenly; transferring a certain volume of fluorescent substance solution to the saturated salt solution containing polyethylene glycol and mixing evenly; placing the mixed solution of the above steps into a microwave oven for microwave reaction to a solid powder, and the product is a phosphor. The preparation method is simple, low in economic cost, easy to implement, and the prepared phosphor has good color rendering properties and high yield. However, the preparation method has the following disadvantages: First, the microwave heating speed is fast, which may cause local overheating. If it is not properly controlled, it may cause uneven temperature inside the material, affecting the formation process of the phosphor particles and the final particle size distribution and morphological uniformity, thereby affecting the optical properties. From the Chinese patent CN202010499499.0 Figure 1 and Figure 2 It can be seen that the morphology of the phosphor prepared is not regular and the surface is not smooth; secondly, there is a limitation on the sample quantity, which is not suitable for occasions where a large amount of phosphor needs to be prepared, limiting its application in large-scale production.

[0005] Therefore, how to design a colorful phosphor that is suitable for industrial large-scale production, has a regular morphology, and has high fluorescence quantum yield and fluorescence intensity is a problem to be solved by the present invention. Summary of the invention

[0006] The purpose of the present invention is to provide a multi-color phosphor and its spray drying preparation and application in view of the deficiencies of the prior art. Based on the above problems, the present invention proposes a spray drying preparation method for multi-color phosphor, which has a simple synthesis method, high reaction repeatability and can be expanded for production. The phosphor prepared by this method has excellent optical properties of fluorescent substances, not only realizes efficient solid luminescence, but also creates a way for industrial production.

[0007] The technical solution of the present invention is achieved in this way: A spray drying preparation method for multi-color fluorescent powder comprises the following steps: (1) Preparation of colorful carbon quantum dots; (2) Preparation of colorful carbon quantum dot solution: Place colorful carbon quantum dots in a beaker, add deionized water or anhydrous ethanol, and use a spectrophotometer to adjust the colorful carbon quantum dot solution to a certain absorbance to obtain a colorful carbon quantum dot solution; (3) dialyzing the colorful carbon quantum dot solution in step (2) using a dialysis bag, or mixing the colorful carbon quantum dot solution in step (2) with a carrier solution to obtain a mixed solution; (4) Preparation of colorful phosphors: Setting the parameters of a spray drying device, and under magnetic stirring, sucking the mixed solution in step (3) into the spray drying device through a rubber tube at a uniform speed for spray drying, and collecting the solid powder product, which is the colorful phosphor.

[0008] In the spray-drying preparation method of a colorful phosphor as described above, the colorful carbon quantum dots in step (1) are selected from any one of blue light carbon quantum dots, green light carbon quantum dots, cyan light carbon quantum dots, orange light carbon quantum dots, and red light carbon quantum dots.

[0009] In the above-mentioned spray-drying preparation method of a colorful phosphor, in the step (2), a spectrophotometer is used to adjust the absorbance of the colorful carbon quantum dot solution to 0.05-10.

[0010] In the above-mentioned spray-drying preparation method of a multi-color phosphor, in step (3), the carrier solution is any one of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate, magnesium dodecylbenzene sulfonate, calcium dodecylbenzene sulfonate, polyvinyl pyrrolidone, polyethylene glycol 10000, polyethylene glycol 20000, polyvinyl alcohol, and polyacrylic acid, or any two or more of the aqueous solution or anhydrous ethanol solution.

[0011] In the above-mentioned method for preparing a multi-color phosphor by spray drying, in step (4), the outlet temperature of the spray drying device is set to 80°C to 200°C, the fan speed is set to 50% to 90%, the peristaltic pump speed is set to 8% to 25%, and the striker speed is set to 1s to 2s.

[0012] In the above-mentioned spray-drying preparation method of a colorful phosphor, in the step (3), the carrier solution is a saturated salt solution or a saturated salt solution containing polyethylene glycol; the volume ratio of the colorful carbon quantum dot solution in the step (2) to the saturated salt solution or the saturated salt solution containing polyethylene glycol in the step (3) is (2:1) to (1:15).

[0013] In the above-mentioned spray drying method for preparing a colorful phosphor, in the step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

[0014] Based on the same inventive concept, the present invention provides a multi-colored phosphor, which is prepared using the spray drying preparation method as described above.

[0015] The colorful phosphor as described above is a blue light phosphor having an emission peak wavelength of 420 to 500 nm in the excitation wavelength range of 340 to 420 nm, or a yellow-green light phosphor having an emission peak wavelength of 520 to 550 nm in the excitation wavelength range of 420 to 500 nm, or an orange light phosphor having an emission peak wavelength of 580 to 620 nm in the excitation wavelength range of 460 to 560 nm, or a red light phosphor having an emission peak wavelength of 590 to 680 nm in the excitation wavelength range of 460 to 580 nm.

[0016] Based on the same inventive concept, the present invention provides a method for preparing colorful phosphors as described above or an application of the colorful phosphors as described above, wherein the colorful phosphors are used to prepare display devices, laser lighting, LED lighting or luminous materials.

[0017] The beneficial effects of the present invention are: 1. The spray-drying preparation method of a colorful phosphor provided by the present invention has milder reaction conditions compared with the preparation methods in the prior art, especially compared with the microwave method, and can protect the structure of the colorful phosphor from high temperature damage. Especially for heat-sensitive components, it is easier to retain the structure of the carrier itself, which helps to improve the uniformity and optical properties of the colorful phosphor.

[0018] 2. The spray drying preparation method of the colorful fluorescent powder provided by the present invention has a fast drying speed, reduces the heating time of the material, effectively reduces energy consumption and production cycle, reduces costs, and is suitable for large-scale continuous production.

[0019] 3. The colorful phosphor provided by the present invention has a relatively regular morphology and a smooth surface. The regular morphology and smooth surface are conducive to the uniform scattering and reflection of light, reducing light scattering loss, thereby improving the luminous efficiency and brightness of the phosphor, and can produce purer and more saturated colors, and maintain color consistency under different viewing angles and long-term use, which is particularly important for applications requiring high color reproduction and long-term stability.

[0020] 4. The colorful phosphor prepared by the spray drying method of the present invention has the advantages of being environmentally friendly, low cost, and easy to obtain, and can be used to prepare display devices, laser lighting, LED lighting, or luminous materials. The blue LED (B-LED), green LED (G-LED), orange LED (O-LED), and red LED (R-LED) prepared by the colorful phosphor of the present invention can produce bright blue light, green light, orange-red light, and red light; the white light LED (WLED) prepared by the colorful phosphor of the present invention emits almost the entire visible light region (400~720 nm), and the LED device emits bright white light when powered on, which illustrates the potential of the spray drying method in preparing high-performance phosphors, which creates conditions for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the phosphor BCDs / NaCl-1 prepared in Comparative Example 1; Figure 2 The scanning electron microscope images of the phosphor BCDs / NaCl-2 prepared in Example 1, wherein the scale bar of (A) is 1 μm, and the scale bar of (B) is 5 μm; Figure 3 Transmission electron microscope images of the phosphor BCDs / NaCl-2 prepared in Example 1 at different angles, wherein the scale bars of (A) and (B) are both 500 nm; Figure 4 Fourier infrared spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5; Figure 5 It is a comparison chart of X-ray diffraction spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5; Figure 6 (A) is a comparison chart of the fluorescence intensity and quantum yield of the blue light phosphors prepared in Example 1, Example 7 and Comparative Example 1 at different outlet temperatures; Figure 6 (B) is a comparison chart of the fluorescence intensity and quantum yield of the blue light phosphor prepared in Example 1 and Example 8 by changing the volume ratio of a B-CDs solution with an absorbance of 0.5 and a saturated sodium chloride solution; Figure 7 It is a comparison chart of the fluorescence intensity of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5; Figure 8 The fluorescence spectrum of the blue phosphor BCDs / NaCl-2 prepared in Example 1; Fig. 9 This is a scanning electron microscope image of the yellow-green phosphor GCDs / PEG400 / NaCl-1 prepared in Comparative Example 3; Fig.10 Scanning electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles, wherein the scale bars of (A) and (B) are both 5 μm, and the scale bar of (C) is 3 μm; Fig.11 Transmission electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles. The scale bars of (A), (B) and (C) are all 500 nm. Fig.12 X-ray diffraction spectra of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 and the phosphor G-CDspowder prepared in Example 6; Fig.13 Fourier transform infrared spectra of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 and the phosphor G-CDspowder prepared in Example 6; Fig.14 This is a comparison chart of the fluorescence intensity and quantum yield of the green phosphors prepared in Example 2 and Example 9 at different outlet temperatures; Fig.15 This is a comparison chart of the fluorescence intensity and quantum yield of the green phosphors prepared in Example 2 and Example 10 at different PEG400 contents; Fig.16 This is a comparison chart of the fluorescence intensity and quantum yield of the green phosphors prepared in Example 2 and Example 11 at different ratios of GCDs and NaCl; Fig.17 It is a fluorescence intensity comparison diagram of the phosphor powder GCDs / PEG400 / NaCl-2 prepared in Example 2, the phosphor powder GCDs / NaCl-2 prepared in Comparative Example 2, and the phosphor powder GCDs powder prepared in Example 6; Fig.18 The fluorescence spectrum of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2; Fig.19 This is a scanning electron microscope image of the orange phosphor OCDs / PEG400 / NaCl-1 prepared in Comparative Example 6; Fig. 20 Scanning electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles, wherein the scale bars of (A) and (B) are both 5 μm; Fig.21Transmission electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles, wherein the scale bars of (A) and (B) are both 500 nm; Fig. 22 A comparison chart of X-ray diffraction spectra of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the phosphor OCDs / NaCl-2 prepared in Comparative Example 5; Fig.23 A comparison chart of the fluorescence intensity of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the phosphor OCDs / NaCl-2 prepared in Comparative Example 5; Fig.24 The fluorescence spectrum of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3; Fig.25 The fluorescence spectrum of the phosphor RCDs@PVP prepared in Example 4; Fig.26 Emission spectra of blue LED (B-LED), green LED (G-LED), orange LED (O-LED) and red LED (R-LED) prepared using the blue phosphor BCDs / NaCl-2 prepared in Example 1, the green phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the red phosphor RCDs@PVP prepared in Example 4; wherein, (A) B-LED; (B) G-LED; (C) O-LED and (D) R-LED devices are photographed after power is applied; (E) CIE coordinates of B-LED, G-LED, O-LED and R-LED; (F) emission spectra of B-LED, (G) G-LED, (H) O-LED and (I) R-LEDs; Fig. 27 The optical properties of white light LEDs (WLEDs) prepared using the blue phosphor BCDs / NaCl-2 prepared in Example 1, the green phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3, and the red phosphor RCDs@PVP prepared in Example 4; wherein (A) CIE coordinates of the WLED, (B) emission spectrum of the WLED, and the inset is a photo of the light emission of the WLED after power is supplied. DETAILED DESCRIPTION

[0022] The following will combine the contents in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0026] The present invention provides a method for preparing a multi-color fluorescent powder by spray drying, comprising the following steps: A spray drying preparation method for multi-color fluorescent powder comprises the following steps: (1) Preparation of colorful carbon quantum dots; (2) Preparation of colorful carbon quantum dot solution: Place colorful carbon quantum dots in a beaker, add deionized water or anhydrous ethanol, and use a spectrophotometer to adjust the colorful carbon quantum dot solution to a certain absorbance to obtain a colorful carbon quantum dot solution; (3) dialyzing the colorful carbon quantum dot solution in step (2) using a dialysis bag, or mixing the colorful carbon quantum dot solution in step (2) with a carrier solution to obtain a mixed solution; (4) Preparation of multi-color phosphor: Setting the parameters of the spray drying device, under magnetic stirring, the mixed solution in step (3) is uniformly sucked into the spray drying device through a rubber tube for spray drying, so that it is atomized into small particles in the high-speed airflow, and then quickly dried to a solid powder product, and the solid powder product is collected. The product is the multi-color phosphor.

[0027] Preferably, the colorful carbon quantum dots in step (1) are selected from any one of blue light carbon quantum dots, green light carbon quantum dots, cyan light carbon quantum dots, orange light carbon quantum dots, and red light carbon quantum dots.

[0028] The "carrier" in the present invention refers to a substance used to carry and disperse colorful carbon quantum dots, which enables uniform particles to be formed during the spray drying process. Preferably, in the step (3), the carrier solution is any one of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate, magnesium dodecylbenzene sulfonate, calcium dodecylbenzene sulfonate, polyvinyl pyrrolidone, polyethylene glycol 10000, polyethylene glycol 20000, polyvinyl alcohol, polyacrylic acid, or any two or more aqueous solutions or anhydrous ethanol solutions.

[0029] In some preferred embodiments of the present invention, colorful carbon quantum dots are added to a saturated salt solution or a mixed solution of a saturated salt solution containing polyethylene glycol and mixed evenly, and corresponding process parameters are set through a spray drying device, so that the colorful carbon quantum dots are embedded in the salt ion crystals, so that the particle distance between the colorful carbon quantum dots is increased; in addition, the polyethylene glycol and the saturated salt solution work together to protect the luminescence center of the colorful carbon quantum dots, thereby realizing the photoluminescence of the colorful carbon quantum dots in the solid state.

[0030] In some preferred embodiments of the present invention, in step (2), the absorbance of the colorful carbon quantum dot solution is adjusted to 0.05-10 using a spectrophotometer. Preferably, in step (2), the absorbance of the colorful carbon quantum dot solution is adjusted to 0.2-5 using a spectrophotometer. If the absorbance of the colorful carbon quantum dot solution is too low, lower than 0.2, the luminescence intensity of the prepared phosphor will not be high enough; if the absorbance of the colorful carbon quantum dot solution is too high, higher than 5, it will affect the self-absorption of the prepared phosphor and the luminescence of the fluorescent substance. Preferably, in step (2), the absorbance of the colorful carbon quantum dot solution is adjusted to 0.5-2.5 using a spectrophotometer. Based on this absorbance, in step (3), the carrier solution is a saturated salt solution or a saturated salt solution containing polyethylene glycol; the volume ratio of the colorful carbon quantum dot solution in step (2) to the saturated salt solution or the saturated salt solution containing polyethylene glycol in step (3) is (2:1) to (1:15).

[0031] Optionally, when the absorbance of the colorful carbon quantum dot solution is adjusted to 0.5-2.5 using a spectrophotometer, the volume ratio of the colorful carbon quantum dot solution in step (2) to the saturated salt solution in step (3) is 1:1. Optionally, when the absorbance of the colorful carbon quantum dot solution is adjusted to 0.5-2.5 using a spectrophotometer, the volume ratio of the colorful carbon quantum dot solution in step (2) to the saturated salt solution containing polyethylene glycol in step (3) is 1:3-1:10. Under this condition, on the one hand, the luminous intensity of the prepared phosphor can be guaranteed, and on the other hand, the preparation yield of the phosphor is improved, providing a direction for realizing industrial production.

[0032] In some preferred embodiments of the present invention, when the volume ratio of BCDs solution (Abs=0.5) to saturated sodium chloride solution is 1:1, the blue light fluorescence quantum yield and fluorescence intensity reach the maximum.

[0033] In some preferred embodiments of the present invention, when the volume ratio of the GCDs solution (Abs=1.25) to the saturated sodium chloride solution with a PEG400 content of 6% is 1:3, the green fluorescence intensity is the highest.

[0034] Optionally, the mass fraction of polyethylene glycol in the saturated salt solution containing polyethylene glycol in step (3) is 2% to 10%. Preferably, the mass fraction of polyethylene glycol in the saturated salt solution containing polyethylene glycol in step (3) is 6%.

[0035] In some preferred embodiments of the present invention, in step (4), the outlet temperature of the spray drying device is set to 80°C to 200°C, the fan speed is set to 50% to 90%, the peristaltic pump speed is set to 8% to 25%, and the impact needle speed is set to 1s to 2s. Under these conditions, the use of the spray drying method provides relatively mild reaction conditions, avoids the damage to the morphology and structure of the phosphor by the violent reaction conditions, greatly improves the yield of the phosphor, simplifies the preparation process of the phosphor; at the same time, it creates conditions for industrial production. This method is simple to operate, has a high repetition rate, low cost, and is environmentally friendly. Preferably, in step (4), the outlet temperature of the spray drying device is set to 100°C to 120°C. Optionally, the outlet temperature of the spray drying device is set to 120°C, and the fluorescence intensity of the prepared blue light phosphor is the largest, and the quantum yield is close to the highest; optionally, the outlet temperature of the spray drying device is set to 100°C, and the fluorescence intensity of the prepared green light phosphor is the largest, and the quantum yield is close to the highest.

[0036] Most preferably, in step (4), the outlet temperature of the spray drying device is set to 120° C., the fan speed is set to 90%, the peristaltic pump speed is set to 15%, and the impactor speed is set to 2 s.

[0037] Preferably, in step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

[0038] Based on the same inventive concept, the present invention provides a multi-colored phosphor, which is prepared using the spray drying preparation method as described above.

[0039] The colorful phosphor as described above is a blue light phosphor having an emission peak wavelength of 420 to 500 nm in the excitation wavelength range of 340 to 420 nm, or a yellow-green light phosphor having an emission peak wavelength of 520 to 550 nm in the excitation wavelength range of 420 to 500 nm, or an orange light phosphor having an emission peak wavelength of 580 to 620 nm in the excitation wavelength range of 460 to 560 nm, or a red light phosphor having an emission peak wavelength of 590 to 680 nm in the excitation wavelength range of 460 to 580 nm. Preferably, the colorful phosphor is a blue light phosphor having an emission peak wavelength of 427 nm at an ultraviolet excitation wavelength of 360 nm, or a yellow-green light phosphor having an emission peak wavelength of 535 nm at an excitation wavelength of 500 nm, or an orange light phosphor having an emission peak wavelength of 602 nm at an excitation wavelength of 560 nm, or a red light phosphor having an emission peak wavelength of 603 nm at an excitation wavelength of 560 nm.

[0040] Based on the same inventive concept, the present invention provides a multi-color phosphor prepared by the preparation method as described above or an application of the multi-color phosphor as described above, wherein the multi-color phosphor is used to prepare a display device, laser lighting, LED lighting or luminous material. Preferably, the multi-color phosphor is used to prepare LED lighting, such as blue LED, green LED, orange LED, red LED and white LED.

[0041] The blue LED (B-LED), green LED (G-LED), orange LED (O-LED) and red LED (R-LED) prepared by the present invention can generate bright blue light, green light, orange-red light and red light. The emission bands are located at 431 nm, 527 nm, 600 nm, 613 nm and 657 nm respectively.

[0042] Preferably, the LED lighting is a white light LED (WLED), wherein the mass ratio of blue light phosphor, green light phosphor, orange light phosphor and red light phosphor is 2:2:1:1, the emission covers almost the entire visible light region (400~720 nm), and the LED device emits bright white light when powered on.

[0043] Example 1 1. Preparation of blue carbon quantum dots: 0.08 g of phthalonitrile and 1.0 g of citric acid were dissolved in 20.0 mL of 0.8 M sodium hydroxide solution. Subsequently, the solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally heated at 180 ° C for 8 h. After naturally cooling to room temperature, the light yellow solution was neutralized with dilute hydrochloric acid solution and the pH was adjusted to 7 to obtain a light blue solution, which is blue carbon quantum dots, hereinafter referred to as B-CDs.

[0044] 2. Preparation of the blue phosphor (BCDs / NaCl-2) of this embodiment: (1) Preparation of B-CDs solution: Place the B-CDs solution in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of B-CDs to 0.5 to obtain the desired B-CDs solution.

[0045] (2) Preparation of saturated sodium chloride solution: At room temperature, weigh 180 g of sodium chloride solid and add 500 mL of deionized water to completely dissolve it to obtain a saturated sodium chloride solution.

[0046] (3) Preparation of blue phosphor: 250 mL of saturated sodium chloride solution and 250 mL of B-CDs solution with an absorbance of 0.5 were measured and mixed evenly to obtain a mixed solution; the parameters of the spray drying device were set, the outlet temperature of the spray drying device was set to 120 °C, the fan speed was set to 90%, the peristaltic pump speed was set to 15%, and the impact needle speed was set to 2 s. At the same time, the stirring rate of the mixed solution of B-CDs and saturated sodium chloride was maintained at 900 rpm on the magnetic stirrer, and the mixed solution was uniformly sucked into the device through a rubber tube for spray drying. After the mixed solution was spray dried, the solid powder in the collection bottle was collected into a wide-mouth bottle to obtain a blue phosphor, which was named BCDs / NaCl-2.

[0047] The fluorescence quantum yield of the blue light phosphor prepared in Example 1 of the present invention was tested by using an Edinburgh fluorescence spectrometer FLS1000. The fluorescence quantum yield of the blue light phosphor prepared in Example 1 of the present invention was 48.95%.

[0048] Example 2 1. Preparation of green carbon quantum dots: 0.5 g of phthalonitrile and 0.3 g of resorcinol were dissolved in 15.0 mL of 1.2 M sodium hydroxide solution. Subsequently, it was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and solvothermally heated at 200 ° C for 8 h. After naturally cooling to room temperature, a certain concentration of dilute hydrochloric acid solution was used for neutralization, and the pH was adjusted to 7 to obtain a green solution, namely green carbon quantum dots, hereinafter referred to as G-CDs.

[0049] 2. Preparation of green phosphor (GCDs / PEG400 / NaCl-2) in this embodiment: (1) Preparation of G-CDs solution: Place the G-CDs solution in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of G-CDs to 1.25 to obtain the desired G-CDs solution.

[0050] (2) Preparation of sodium chloride solution containing polyethylene glycol: Prepare 500 mL of saturated sodium chloride solution at room temperature, then add polyethylene glycol 400 (hereinafter referred to as PEG400) to the saturated sodium chloride solution to make the saturated sodium chloride solution contain 6% by mass of PEG400, and stir evenly.

[0051] (3) Preparation of green phosphor: 375 mL of saturated sodium chloride solution containing 6% PEG400 and 125 mL of G-CDs solution with an absorbance of 1.25 were mixed evenly to obtain a mixed solution; the parameters of the spray drying device were set, the outlet temperature of the spray drying device was set to 100 °C, the fan speed was set to 90%, the peristaltic pump speed was set to 15%, and the impact needle speed was set to 2 s. At the same time, the stirring rate of the mixed solution of G-CDs and saturated sodium chloride was maintained at 900 rpm on the magnetic stirrer, and the mixed solution was uniformly sucked into the device through a rubber tube for spray drying. After the mixed solution was spray dried, the solid powder in the collection bottle was collected into a wide-mouth bottle to obtain green phosphor, which was named GCDs / PEG400 / NaCl-2.

[0052] The determination method of Example 1 was used to test the fluorescence quantum yield of the green phosphor prepared in Example 2 of the present invention. The test result showed that the fluorescence quantum yield of the green phosphor prepared in Example 2 of the present invention was 49.23%.

[0053] Example 3 1. Preparation of orange-light carbon quantum dots: 1.0 mL of polyethylene glycol 400 and 30.0 mg of RhB were dissolved in 15.0 mL of anhydrous ethanol. Subsequently, the RhB solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and solvothermally heated at 180 ° C for 8 h. After cooling naturally to room temperature, an orange-red solution was obtained, which was orange-light carbon quantum dots, hereinafter referred to as O-CDs.

[0054] 2. Preparation of the orange phosphor (OCDs / PEG400 / NaCl-2) of this embodiment: (1) Preparation of O-CDs solution: Place the O-CDs solution in a beaker, add anhydrous ethanol solution, and use a spectrophotometer to adjust the absorbance of O-CDs to 2.5 to obtain the desired O-CDs solution.

[0055] (2) Preparation of sodium chloride solution containing polyethylene glycol: Prepare 500 mL of saturated sodium chloride solution at room temperature, then add PEG400 to the saturated sodium chloride solution to make the saturated sodium chloride solution contain 6% by mass of PEG400, and stir evenly.

[0056] (3) Preparation of orange phosphor: 400 mL of saturated sodium chloride solution containing 6% PEG400 and 40 mL of O-CDs solution with an absorbance of 2.5 were mixed evenly to obtain a mixed solution; the parameters of the spray drying device were set, the outlet temperature of the spray drying device was set to 120 °C, the fan speed was set to 90%, the peristaltic pump speed was set to 15%, and the impact needle speed was set to 2s. At the same time, the stirring rate of the mixed solution of O-CDs and saturated sodium chloride was maintained at 900 rpm on the magnetic stirrer, and the mixed solution was uniformly sucked into the device through a rubber tube for spray drying. After the mixed solution was spray dried, the solid powder in the collection bottle was collected into a wide-mouth bottle to obtain orange phosphor, which was named OCDs / PEG400 / NaCl-2.

[0057] The determination method of Example 1 was used to test the fluorescence quantum yield of the orange phosphor prepared in Example 3 of the present invention. The test result showed that the fluorescence quantum yield of the orange phosphor prepared in Example 3 of the present invention was 54.41%.

[0058] Example 4 1. Preparation of red light carbon quantum dots: Weigh 0.108g of o-phenylenediamine and 0.346g of p-aminobenzenesulfonic acid in a mortar and grind for 3 min to mix them thoroughly and form fine powder. Then transfer the ground powder to a polytetrafluoroethylene liner and react in an electric heated blast drying oven at 200 °C for 8 h. After the reactor is cooled to room temperature, fluffy black powder is obtained. The black powder is washed three times with water (centrifuged three times at 10,000 rpm, 5 min each time) to remove the generated acid. Finally, put it in a 60 °C oven to dry to obtain black powder, which is red light carbon quantum dots, hereinafter referred to as R-CDs.

[0059] 2. Preparation of the red phosphor of this embodiment: (1) Preparation of R-CDs solution: Weigh 5 mg of R-CDs powder into a beaker, add it to 20 mL of anhydrous ethanol, and dissolve it by ultrasonication at 30°C for 20 min. Filter the solution through a 0.22 µm filter membrane to remove large particles to obtain the desired R-CDs solution. Use a spectrophotometer to adjust the absorbance of the R-CDs solution to 1.5.

[0060] (2) Preparation of red phosphor: Weigh 25 g of polyvinyl pyrrolidone (PVP) as a dispersant for carbon dots, add it to anhydrous ethanol containing RCDs, stir to completely dissolve it, and obtain a mixed solution; set the parameters of the spray drying device, the outlet temperature of the spray drying device is set to 120 °C, the fan speed is set to 90%, the peristaltic pump speed is set to 15%, and the impact needle speed is set to 2 s. At the same time, the stirring rate of the mixed solution of R-CDs and anhydrous ethanol is maintained at 900 rpm on the magnetic stirrer, and the mixed solution is uniformly sucked into the device through a rubber tube for spray drying. After the mixed solution is spray dried, the solid powder in the collection bottle is collected into a wide-mouth bottle to obtain red phosphor, which is named RCDs@PVP.

[0061] The determination method of Example 1 was used to test the fluorescence quantum yield of the red phosphor prepared in Example 4 of the present invention. The test result showed that the fluorescence quantum yield of the red phosphor prepared in Example 4 of the present invention was 20.28%.

[0062] Example 5 1. Preparation of blue carbon quantum dots: 0.08 g of phthalonitrile and 1.0 g of citric acid were dissolved in 20.0 mL of 0.8 M sodium hydroxide solution. Subsequently, the solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally heated at 180 ° C for 8 h. After naturally cooling to room temperature, the light yellow solution was neutralized with dilute hydrochloric acid solution and the pH was adjusted to 7 to obtain a light blue solution, which is blue carbon quantum dots, hereinafter referred to as B-CDs.

[0063] 2. Preparation of blue fluorescent powder (BCDs powder) in this embodiment: (1) Preparation of B-CDs solution: Place the B-CDs solution in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of B-CDs to 0.5 to obtain the desired B-CDs solution.

[0064] (2) Preparation of blue phosphor: The BCDs solution was dialyzed for 8 hours using a dialysis bag with a specification of 1000Da to obtain a dialyzed B-CDs solution; the parameters of the spray drying device were set, the outlet temperature of the spray drying device was set to 120°C, the fan speed was set to 90%, the peristaltic pump speed was set to 15%, and the impact needle speed was set to 2 s. At the same time, the stirring rate of the dialyzed B-CDs solution was maintained at 900 rpm on the magnetic stirrer, so that the dialyzed B-CDs solution was uniformly sucked into the device through a rubber tube for spray drying. After the solution was spray dried, the solid powder in the collection bottle was collected into a wide-mouth bottle to obtain a blue phosphor, which was named BCDs powder.

[0065] The fluorescence quantum yield of the blue light phosphor prepared in Example 5 of the present invention was tested by using an Edinburgh fluorescence spectrometer FLS1000. The fluorescence quantum yield of the blue light phosphor prepared in Example 5 of the present invention was 5.06%.

[0066] Example 6 1. Preparation of green carbon quantum dots: 0.5 g of phthalonitrile and 0.3 g of resorcinol were dissolved in 15.0 mL of 1.2 M sodium hydroxide solution. Subsequently, it was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and solvothermally heated at 200 ° C for 8 h. After naturally cooling to room temperature, a certain concentration of dilute hydrochloric acid solution was used for neutralization, and the pH was adjusted to 7 to obtain a green solution, namely green carbon quantum dots, hereinafter referred to as G-CDs.

[0067] 2. Preparation of green phosphor (GCDs powder) in this example (1) Preparation of G-CDs solution: Place the G-CDs solution in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of B-CDs to 1.25 to obtain the desired G-CDs solution.

[0068] (2) Preparation of green phosphor: GCDs solution was dialyzed for 8 hours using a dialysis bag with a specification of 1000Da to obtain a dialyzed G-CDs solution; the parameters of the spray drying device were set, the outlet temperature of the spray drying device was set to 120 °C, the fan speed was set to 90%, the peristaltic pump speed was set to 15%, and the impact needle speed was set to 2 s. At the same time, the stirring rate of the dialyzed G-CDs solution was maintained at 900 rpm on the magnetic stirrer, so that the dialyzed G-CDs solution was uniformly sucked into the device through a rubber tube for spray drying. After the solution was spray dried, the solid powder in the collection bottle was collected into a wide-mouth bottle to obtain green phosphor, which was named GCDs powder.

[0069] The fluorescence quantum yield of the green phosphor prepared in Example 6 of the present invention was tested by using an Edinburgh fluorescence spectrometer FLS1000. The fluorescence quantum yield of the green phosphor prepared in Example 6 of the present invention was 0.08%.

[0070] Example 7 The method is basically the same as Example 1, except that the outlet temperature of the spray drying device is changed to 80°C, 100°C, 150°C, and 180°C. The quantum yield and fluorescence intensity are tested using the method of Example 1. The results are as follows: Figure 6 As shown in A.

[0071] Example 8 The method is basically the same as Example 1, except that the volume ratio of the B-CDs solution with an absorbance of 0.5 and the saturated sodium chloride solution is changed to 2:1, 1:3, 1:5, 1:7, and 1:11. The quantum yield and fluorescence intensity are tested using the method of Example 1. The results are as follows: Figure 6 As shown in B.

[0072] Example 9 The method is basically the same as Example 2, except that the outlet temperature of the spray drying device is changed to 80°C, 120°C, 150°C, and 200°C. The quantum yield and fluorescence intensity are tested using the method of Example 2. The results are as follows: Fig.14 shown.

[0073] Example 10 The method is basically the same as Example 2, except that the mass fraction of PEG400 in the saturated sodium chloride solution containing PEG400 is changed to 2%, 4%, 8%, and 10%. The quantum yield and fluorescence intensity are tested using the determination method of Example 2, and the results are as follows: Fig.15 shown.

[0074] Embodiment 11 The method is basically the same as Example 2, except that the volume ratio of the G-CDs solution with an absorbance of 1.25 and the saturated sodium chloride solution containing 6% PEG400 is changed to 1:2, 1:4, 1:5, 1:7, and 1:10. The quantum yield and fluorescence intensity are tested using the determination method of Example 2, and the results are as follows: Fig.16 shown.

[0075] Comparative Example 1: The preparation method of the blue light phosphor used in this comparative example is different from that in Example 1, specifically, the spray drying method is replaced by a microwave method, wherein the volume ratio of the B-CDs solution with an absorbance of 0.5 and the saturated sodium chloride solution is changed from 1:1 to 1:3, and the equipment is replaced by a microwave oven with a power of 700 W, a microwave operating frequency of 2450 MHz, and a reaction time of 1.5 min. After cooling to room temperature, the phosphor is taken out and collected to obtain the phosphor. The phosphor prepared by this method is named BCDs / NaCl-1.

[0076] Comparative Example 2: The preparation method of the yellow-green phosphor in this comparative example is basically the same as that in Example 2, except that PEG400 is not added in the preparation step of the yellow-green phosphor. The phosphor prepared by this method is named GCDs / NaCl-2.

[0077] Comparative Example 3: The preparation method of the yellow-green phosphor used in this comparative example is different from that in Example 2, specifically, the spray drying method is replaced by a microwave method, the equipment is replaced by a microwave oven, the power of the microwave oven is 700 W, the microwave operating frequency is 2450 MHz, the reaction time is 1.5 min, and after cooling to room temperature, it is taken out and collected to obtain the phosphor. The phosphor prepared by this method is named GCDs / PEG400 / NaCl-1.

[0078] Comparative Example 4: The preparation method of the yellow-green phosphor in this comparative example is basically the same as that of comparative example 3, except that PEG400 is not added in the preparation step of the yellow-green phosphor. The phosphor prepared by this method is named GCDs / NaCl-1.

[0079] Comparative Example 5: The preparation method of the orange phosphor in this comparative example is basically the same as that in Example 3, except that PEG400 is not added in the preparation step of the orange phosphor. The phosphor prepared by this method is named OCDs / NaCl-2.

[0080] Comparative Example 6: The preparation method of the orange phosphor used in this comparative example is different from that in Example 3, specifically, the spray drying method is replaced by a microwave method, wherein the volume ratio of the O-CDs solution with an absorbance of 2.5 and the saturated sodium chloride solution containing 6% polyethylene glycol 400 is replaced from 1:10 to 1:12; the content of PEG400 remains unchanged at 6%; the equipment is replaced by a spray drying equipment by a microwave oven, the power of the microwave oven is 700 W, the microwave operating frequency is 2450 MHz, the reaction time is 1.5 min, and after cooling to room temperature, it is taken out and collected to obtain the phosphor. The phosphor prepared by this method is named OCDs / PEG400 / NaCl-1.

[0081] Comparative Example 7: The preparation method of the orange phosphor in this comparative example is basically the same as that of comparative example 6, except that PEG400 is not added in the preparation step of the orange phosphor. The phosphor prepared by this method is named OCDs / NaCl-1.

[0082] Application Example 1: The blue light phosphor BCDs / NaCl-2 prepared in Example 1, the green light phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange light phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the red light phosphor RCDs@PVP prepared in Example 4 were used to prepare blue light LED (B-LED), green light LED (G-LED), orange light LED (O-LED) and red light LED (R-LED), respectively.

[0083] The phosphor BCDs / NaC1-2 prepared by the present invention is used as a fluorescent conversion layer for encapsulating blue light LEDs, and a special LED chip with an emission peak of 365 nm is selected as an excitation source to make a blue light LED light-emitting device. The encapsulation process is as follows: First, 0.2g of modified acrylate adhesive A and 0.2g of modified acrylate adhesive B are uniformly mixed with 0.1g of BCDs / NaC1-2, and uniformly coated on a special LED chip with an excitation wavelength of 365 nm, and then cured at room temperature for 4h to obtain a blue light-emitting LED, recorded as B-LED, and then relevant tests are carried out under the condition that the driving voltage of the chip is 3V. Among them, modified acrylate adhesive A and modified acrylate adhesive B are purchased from Gelianghao New Materials Co., Ltd., and the specifications are: boxed AB80g (A40g+B40g).

[0084] The preparation process and test conditions of the G-LED prepared by the present invention are basically the same as those of the B-LED, except that the blue light phosphor BCDs / NaCl-2 is replaced by the green light phosphor GCDs / PEG400 / NaCl-2.

[0085] The preparation process and test conditions of the O-LED prepared by the present invention are basically the same as those of the B-LED, except that the blue light phosphor BCDs / NaC1-2 is replaced by the orange light phosphor OCDs / PEG400 / NaC1-2, and the LEDs dedicated chip with an emission peak of 365 nm is replaced by the LEDs dedicated chip with an emission peak of 490 nm.

[0086] The preparation process and test conditions of the R-LED prepared by the present invention are basically the same as those of the B-LED, except that the blue light phosphor BCDs / NaC1-2 is replaced by the red light phosphor RCDs@PVP.

[0087] The test performance results are as follows: Fig.26 shown.

[0088] Application Example 2: White light LED (WLED) was prepared using the blue phosphor BCDs / NaCl-2 prepared in Example 1, the green phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3, and the red phosphor RCDs@PVP prepared in Example 4, wherein the mass ratio of BCDs / NaCl-2, GCDs / PEG400 / NaCl-2, OCDs / PEG400 / NaCl-2 and RCDs@PVP was 2:2:1:1.

[0089] The mass ratios of the blue phosphor BCDs / NaCl-2, green phosphor GCDs / PEG400 / NaCl-2, orange phosphor OCDs / PEG400 / NaCl-2 and red phosphor RCDs@PVP prepared by the present invention are adjusted and mixed with modified acrylate adhesive A and modified acrylate adhesive B to serve as the fluorescent conversion layer of WLED. The specific operation is as follows: First, 0.3g of modified acrylate adhesive A and 0.3g of modified acrylate adhesive B are evenly mixed, and then BCDs / NaC1-2, GCDs / PEG400 / NaC1-2, OCDs / PEG400 / NaC1-2 and RCDs@PVP are evenly mixed in a mass ratio of 2:2:1:1 and added. Specifically, the mass of BCDs / NaC1-2 is 0.2g, the mass of GCDs / PEG400 / NaC1-2 is 0.2g, the mass of OCDs / PEG400 / NaC1-2 is 0.1g, and the mass of RCDs@PVP is 0.1g; then apply it on a dedicated LED chip with an excitation wavelength of 365nm, cure it at room temperature for 4h, and obtain a white light LED, recorded as WLED, and then carry out relevant tests under the condition that the chip driving voltage is 3V. Among them, modified acrylate adhesive A and modified acrylate adhesive B were purchased from Gelianghao New Materials Co., Ltd. with the specifications of: boxed AB80g (A40g+B40g).

[0090] The test performance results are as follows: Fig. 27 shown.

[0091] Figure 1 This is a scanning electron microscope image of the phosphor BCDs / NaCl-1 prepared in Comparative Example 1. It can be seen from the image that the morphology of the phosphor BCDs / NaCl-1 prepared by the microwave method presents a cubic structure, but the crystal structure is destroyed.

[0092] Figure 2 This is a scanning electron microscope image of the phosphor BCDs / NaCl-2 prepared in Example 1. Figure 2 A and Figure 2As can be seen from B, the morphology of the phosphor prepared by spray drying is relatively regular, and BCDs / NaCl-2 presents the crystal structure of sodium chloride, all of which are cubic structures and have a smooth surface, indicating that BCDs are capped in the sodium chloride crystals.

[0093] Figure 3 Transmission electron microscope images of the phosphor BCDs / NaCl-2 prepared in Example 1 at different angles. Figure 3 A and Figure 3 In B, it can be observed that B-CDs are evenly distributed in the sodium chloride crystals.

[0094] Figure 4 The Fourier infrared spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5 show that B-CDs has absorption peaks at 1567 cm-1, 3356 cm-1, 1391 cm-1, 1243 cm-1 and 1057 cm-1, which correspond to the stretching vibrations of C=N, -OH, -COO-, COC and CO, respectively. By comparison, it is found that the absorption band of BCDs / NaCl-2 is consistent with that of BCDs, indicating that after BCDs is embedded in sodium chloride crystals, its surface groups are retained and not damaged. It also shows that infrared light can pass through sodium chloride crystals.

[0095] Figure 5 The X-ray diffraction spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5 are compared. It can be seen from the figure that the diffraction peak position of the phosphor BCDs / NaCl-2 prepared in Example 1 is basically completely consistent with the corresponding NaCl standard card. At the same time, since the diffraction peak intensity of BCDs is weaker than that of NaCl crystals, the diffraction peak of BCDs is not reflected in the phosphor.

[0096] Figure 6 (A) is a comparison chart of the fluorescence intensity and quantum yield of the blue light phosphors prepared in Example 1, Example 7 and Comparative Example 1 at different outlet temperatures; Figure 6 (B) is a comparison chart of the fluorescence intensity and quantum yield of the blue light phosphor prepared in Example 1 and Example 8 by changing the volume ratio of the B-CDs solution with an absorbance of 0.5 and the saturated sodium chloride solution. Figure 6 (A) It can be seen that when the outlet temperature of the device is 120°C, that is, Example 1, the fluorescence intensity of the prepared phosphor is the largest and the quantum yield is the highest. Figure 6(B) It is found that when the volume ratio of BCDs solution (Abs=0.5) to saturated sodium chloride solution is 1:1, that is, Example 1, its fluorescence quantum yield and fluorescence intensity reach the maximum, which are 48.95% and 2616 (au), respectively. Comparing the fluorescence properties of BCDs / NaCl blue phosphors prepared by microwave method and spray drying method, it is found that the fluorescence intensity and fluorescence quantum yield of the blue phosphor BCDs / NaCl-2 prepared by spray drying method in Example 1 are stronger and higher than those of the blue phosphor BCDs / NaCl-1 prepared by microwave method. Therefore, BCDs / NaCl-2 blue phosphor can be mass-produced.

[0097] Figure 7 The fluorescence intensity comparison diagram of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5 is shown in the figure. As can be seen from the figure, the fluorescence intensity of the phosphor prepared in Example 5 is very weak, with a fluorescence intensity of 439 (au), and the fluorescence quantum yield is also low, with a fluorescence quantum yield of 5.06%; when B-CDs is dispersed in the sodium chloride matrix, the fluorescence intensity increases significantly, the fluorescence intensity increases to 2616 (au), and the fluorescence quantum yield also increases to 48.95%.

[0098] Figure 8 The fluorescence spectrum of the blue phosphor BCDs / NaCl-2 prepared in Example 1 is shown in the figure. As can be seen from the figure, the best excitation wavelength of the blue phosphor BCDs / NaCl-2 is 360nm, the emission peak position is 427nm, and the spectrum retains the optical property of BCDs solution excitation independence.

[0099] Fig. 9 This is a scanning electron microscope image of the yellow-green phosphor GCDs / PEG400 / NaCl-1 prepared in Comparative Example 3. It can be seen from the figure that the yellow-green phosphor prepared by the microwave method presents a cubic structure, but the crystal structure is destroyed because the microwave method reaction is too violent.

[0100] Fig.10 The scanning electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles are shown in FIG. Fig.10 A. Fig.10 B and Fig.10 C It can be seen that the morphology of the phosphor prepared by spray drying presents a regular cubic structure. This is because the reaction conditions of the spray drying method are relatively mild and it is easier to retain the structure of the salt crystal itself.

[0101] Fig.11 Transmission electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles. Fig.11 A. Fig.11 B and Fig.11 C It can be seen that the figure not only shows the standard cubic structure of the sodium chloride crystal, but also more clearly shows that GCDs are evenly distributed in the sodium chloride crystal with the assistance of PEG400, indicating that PEG400 is embedded in the NaCl crystal by bonding with GCDs.

[0102] Fig.12 X-ray diffraction spectra of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 and the phosphor G-CDspowder prepared in Example 6. It can be seen from the figure that the diffraction peak position of GCDs / PEG400 / NaCl-2 prepared by spray drying method has a good correspondence with the corresponding standard card of sodium chloride, indicating that the loading of GCDs and PEG400 does not affect the crystallization properties of sodium chloride.

[0103] Fig.13 It is the Fourier infrared spectra of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 and the phosphor G-CDs prepared in Example 6. It can be seen from the figure that in the process of forming G-CDs / PEG400 / NaCl-2, the groups on the surface of GCDs are completely retained. For example, the representative characteristic peaks of -OH, C=N, C=C / CN, and O=CO can all be reflected in GCDs / PEG400 / NaCl-2.

[0104] Fig.14 The fluorescence intensity and quantum yield of the green phosphor prepared in Example 2 and Example 9 at different outlet temperatures are compared. First, the outlet temperature of the spray drying device is optimized. Fig.14 It can be clearly seen that when the outlet temperature of the spray drying device is 100° C., that is, in Example 2, the fluorescence intensity and fluorescence quantum yield of the phosphor both reach the highest, thereby determining the feasibility of the spray drying method for preparing the phosphor.

[0105] Fig.15 The following is a comparison chart of the fluorescence intensity and quantum yield of the green phosphors prepared in Example 2 and Example 10 at different PEG400 contents. Fig.15 It can be obtained that the fluorescence intensity and quantum yield are the highest when the PEG400 content is 6%. In addition, it is observed through experimental phenomena that when the PEG400 content in the saturated sodium chloride solution is higher than 6%, the resulting phosphor is relatively moist. In order not to affect the next application, the best choice is a saturated sodium chloride solution containing 6% PEG400 for spray drying.

[0106] Fig.16The fluorescence intensity and quantum yield comparison of the green phosphor prepared in Example 2 and Example 11 in different volume ratios of G-CDs solution and saturated sodium chloride solution containing 6% PEG400. The absorbance of the GCDs aqueous solution is used to represent its concentration, and the absorbance of GCDs is adjusted to 1.25. Fig.16 As shown, under the same test conditions, when the volume ratio of GCDs solution to saturated sodium chloride solution with a PEG400 content of 6% is 1:3, that is, Example 2, the fluorescence intensity and quantum yield reach the highest, and the optimal volume ratio of GCDs solution to saturated sodium chloride solution with a PEG400 content of 6% is 1:3 for process production.

[0107] Fig.17 The fluorescence intensity comparison diagram of the phosphor powder GCDs / PEG400 / NaCl-2 prepared in Example 2, the phosphor powder GCDs / NaCl-2 prepared in Comparative Example 2 and the phosphor powder GCDs powder prepared in Example 6 is as follows. It can be seen from the figure that the phosphor powder directly prepared from G-CDs in Example 6 has almost no fluorescence, with a fluorescence intensity of 5.6 (au) and a fluorescence quantum yield of 0.08%; for the GCDs / NaCl-2 prepared in Comparative Example 2, when G-CDs is dispersed in a sodium chloride matrix, the fluorescence intensity is very weak, with a fluorescence intensity of 73.9 (au) and a fluorescence quantum yield of 4.56%; however, in Example 2, when PEG400 is present in a saturated sodium chloride solution at a content of 6%, the fluorescence intensity of GCDs / PEG400 / NaCl-2 is greatly increased to 1743 (au), and the fluorescence quantum yield is 49.23%.

[0108] Fig.18 This is the fluorescence spectrum of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2. It can be seen from the figure that this example successfully prepared a yellow-green phosphor with high fluorescence intensity, with the best excitation wavelength at 500nm and the emission peak position at 535nm.

[0109] Fig.19 This is a scanning electron microscope image of the orange phosphor OCDs / PEG400 / NaCl-1 prepared in Comparative Example 6. It can be clearly seen from the image that the NaCl crystal structure in OCDs / PEG400 / NaCl-1 is destroyed, indicating that it is necessary to find milder reaction conditions to retain the crystal structure of sodium chloride.

[0110] Fig. 20 The scanning electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles are shown in FIG. Fig. 20 A and Fig. 20As can be seen from B, the phosphor successfully prepared in this example presents a relatively regular and complete cubic structure of sodium chloride crystals, and has a smooth surface. This is mainly because during spray drying, O-CDs and the saturated sodium chloride solution containing PEG400 are continuously stirred and then uniformly passed through a peristaltic pump into the spray gun of the spray drying equipment. The whole process is relatively gentle, so the degree of damage to the crystal morphology is relatively small.

[0111] Fig.21 Transmission electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles. Fig.21 A and Fig.21 As can be seen from B, OCDs are evenly dispersed inside the sodium chloride crystals. It can be obtained that PEG400 and OCDs form a stable structure by bonding and enter the interior of the sodium chloride crystals, thereby realizing solid-state luminescence.

[0112] Fig. 22 It is a comparison chart of the X-ray diffraction spectra of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the phosphor OCDs / NaCl-2 prepared in Comparative Example 5. It can be seen from the figure that the XRD spectra of the two basically correspond to the main diffraction peaks in the NaCl standard card (JCPDS card number 99-0059), so the embedding of PEG400 and OCDs has no obvious effect on the crystallization properties of sodium chloride.

[0113] Fig.23 The fluorescence intensity comparison diagram of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the phosphor OCDs / NaCl-2 prepared in Comparative Example 5 is shown in the figure. As can be seen from the figure, the fluorescence intensity and fluorescence quantum yield of the phosphor OCDs / NaCl-2 prepared in Comparative Example 5 are relatively low, 124 (au) and 28.32% respectively; however, the introduction of PEG400 makes the fluorescence intensity and quantum yield of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 increase sharply to 1278 (au) and 54.41%; this shows that Example 3 was successfully prepared, and the large-scale preparation of long-wavelength emission phosphors was achieved.

[0114] Fig.24 This is the fluorescence spectrum of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3. As can be seen from the figure, the phosphor OCDs / PEG400 / NaCl-2 retains the optical property of OCDs excitation independence, with the optimal excitation at 560 nm and the emission peak at 602 nm, which realizes the large-scale preparation of solid-state luminescent materials emitting in the long wavelength region and promotes the development of solid-state luminescence of carbon quantum dots in the long wavelength region.

[0115] Fig.25 This is the fluorescence spectrum of the phosphor RCDs@PVP prepared in Example 4, which is prepared with PVP as the matrix and R-CDs as the fluorescent material. It can be seen from the figure that this example successfully prepared a red light phosphor with high fluorescence intensity, with the best excitation wavelength at 560nm and the emission peak position at 603nm.

[0116] Fig.26 The emission spectra of the blue LED (B-LED), green LED (G-LED), orange LED (O-LED) and red LED (R-LED) prepared using the blue phosphor BCDs / NaCl-2 prepared in Example 1, the green phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the red phosphor RCDs@PVP prepared in Example 4. Fig.26 A~ Fig.26 D is a photo of four different colors of LEDs, blue, green, orange-red and red, at 3V. From the photo, we can see that the LEDs produce bright blue, green, orange-red and red light. Fig.26 The CIE1931 coordinates displayed by E are (0.15, 0.12), (0.26, 0.52), (0.56, 0.37) and (0.57, 0.42). Fig.26 F~ Fig.26 I shows the emission spectra of B-LED, G-LED, O-LED and R-LED at 3.0 V, and their emission bands are located at 431 nm, 527 nm, 600 nm, 613 nm and 657 nm, respectively.

[0117] Fig. 27 The optical properties of white light LEDs (WLEDs) prepared using the blue phosphor BCDs / NaCl-2 prepared in Example 1, the green phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2, the orange phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3, and the red phosphor RCDs@PVP prepared in Example 4. Fig. 27 It can be seen that by adjusting the mass ratio of BCDs / NaCl-2, GCDs / PEG400 / NaCl-2, OCDs / PEG400 / NaCl-2 and RCDs@PVP to 2:2:1:1, white LED (WLED) was successfully prepared. Fig. 27 A The CIE of the prepared WLED is (0.30, 0.35), which is close to the CIE 1931 chromaticity coordinates of the standard WLED, and the color temperature is 6947 K; Fig. 27Figure B shows the fluorescence spectrum of WLED at 3V. It can be clearly seen that the emission of the prepared WLED covers almost the entire visible light region (400~720nm) and Fig. 27 The inset of B shows that the LED device emits bright white light when powered on.

[0118] The spray-drying preparation method of a colorful phosphor provided by the present invention is simple to operate, can expand production, and can realize the large-scale process preparation of the phosphor; at the same time, the spray-drying preparation method of a colorful phosphor provided by the present invention greatly improves the yield of the phosphor, shortens the preparation time of the phosphor, and uses low-priced raw materials, which is environmentally friendly.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A spray drying method for preparing colorful fluorescent powder, characterized in that: The following steps are involved: (1) Preparation of colorful carbon quantum dots; (2) Preparation of a colorful carbon quantum dot solution: placing colorful carbon quantum dots in a beaker, adding deionized water or anhydrous ethanol, and using a spectrophotometer to adjust the colorful carbon quantum dot solution to a certain absorbance, thereby obtaining a colorful carbon quantum dot solution; (3) dialyzing the colorful carbon quantum dot solution in step (2) using a dialysis bag, or mixing the colorful carbon quantum dot solution in step (2) with a carrier solution to obtain a mixed solution; (4) Preparation of multi-color phosphor: Setting the parameters of the spray drying device, under magnetic stirring, the mixed solution in step (3) is uniformly sucked into the spray drying device through a rubber tube for spray drying, and the solid powder product is collected. The product is the multi-color phosphor.

2. The spray drying method for preparing a multi-color fluorescent powder according to claim 1, characterized in that: The colorful carbon quantum dots in step (1) are selected from any one of blue light carbon quantum dots, green light carbon quantum dots, cyan light carbon quantum dots, orange light carbon quantum dots, and red light carbon quantum dots.

3. The spray drying method for preparing a multi-color fluorescent powder according to claim 1, characterized in that: In the step (2), the absorbance of the colorful carbon quantum dot solution is adjusted to 0.05-10 using a spectrophotometer.

4. The spray drying method for preparing a multi-color fluorescent powder according to claim 1, characterized in that: In the step (3), the carrier solution is any one of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium fluoride, potassium fluoride, magnesium fluoride, calcium fluoride, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate, magnesium dodecylbenzene sulfonate, calcium dodecylbenzene sulfonate, polyvinyl pyrrolidone, polyethylene glycol 10000, polyethylene glycol 20000, polyvinyl alcohol, and polyacrylic acid, or any two or more of the aqueous solution or anhydrous ethanol solution.

5. The spray drying method for preparing a multi-color fluorescent powder according to claim 1, characterized in that: In the step (4), the outlet temperature of the spray drying device is set to 80° C. to 200° C., the fan speed is set to 50% to 90%, the peristaltic pump speed is set to 8% to 25%, and the impactor speed is set to 1s to 2s.

6. The spray-drying preparation method of a multi-color fluorescent powder according to claim 1, characterized in that: In the step (3), the carrier solution is a saturated salt solution or a saturated salt solution containing polyethylene glycol; the volume ratio of the colorful carbon quantum dot solution in the step (2) to the saturated salt solution in the step (3) or the saturated salt solution containing polyethylene glycol is (2:1) to (1:15).

7. The spray-drying preparation method of a multi-color fluorescent powder according to claim 2, characterized in that: In the step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

8. A colorful fluorescent powder, characterized in that: The method is prepared by the spray drying method according to any one of claims 1 to 7.

9. The multi-colored phosphor according to claim 8, characterized in that: The colorful phosphor is a blue phosphor with an emission peak wavelength of 420 to 500 nm in the excitation wavelength range of 340 to 420 nm, or a yellow-green phosphor with an emission peak wavelength of 520 to 550 nm in the excitation wavelength range of 420 to 500 nm, or an orange phosphor with an emission peak wavelength of 580 to 620 nm in the excitation wavelength range of 460 to 560 nm, or a red phosphor with an emission peak wavelength of 590 to 680 nm in the excitation wavelength range of 460 to 580 nm.

10. A multi-color phosphor prepared by the preparation method according to any one of claims 1 to 7 or a use of the multi-color phosphor according to any one of claims 8 to 9, characterized in that: The colorful fluorescent powder is used for preparing display devices, laser lighting, LED lighting or luminous materials.

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