A multi-colored fluorescent powder and its spray drying preparation method and application

Abstract

The present invention belongs to the field of fluorescent materials. The present invention provides a spray-drying preparation method for multi-color phosphors, comprising the following steps: (1) preparation of multi-color carbon quantum dots; (2) preparation of a multi-color carbon quantum dot solution; (3) dialyzing the multi-color carbon quantum dot solution in step (2) using a dialysis bag, or mixing it with a carrier solution to obtain a mixed solution; (4) preparation of multi-color phosphors: setting the parameters of a spray drying device, and under magnetic stirring, uniformly sucking the mixed solution in step (3) into the spray drying device through a rubber tube for spray drying, collecting a solid powder product, and the product is a multi-color phosphor. The present invention also provides a multi-color phosphor. The present invention also provides an application of the multi-color phosphor, wherein the multi-color phosphor is used to prepare display devices, laser lighting, LED lighting, or luminous materials. The preparation and synthesis method of the phosphors in the present invention is simple, has high reaction repeatability, and can be expanded for production.

Description

Technical Field

[0001] The present 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 multi-color phosphors include high-temperature solid-phase reaction, sol-gel, co-precipitation, and microwave synthesis. The high-temperature solid-phase reaction method involves mixing raw materials such as a matrix material and an activator in proportion, uniformly mixing them through ball milling, and then calcining them at high temperatures to induce a solid-state reaction of the raw materials to form phosphors. However, this method produces a large product particle size, which may require subsequent grinding to improve luminescence and application performance. The operation is cumbersome, and local overheating is prone to occur at high temperatures, affecting the uniformity of the reaction. The sol-gel method involves dissolving a metal alkoxide or an inorganic salt in a solvent to form a precursor solution, which is then hydrolyzed and polymerized to form a sol. After drying and heat treatment, it is converted into phosphor powder. However, this method is prone to form lumps during the drying process, and an additional grinding step is required to obtain powder of the required particle size. Moreover, 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 phosphor powder. This method produces particles that are not very uniform in shape and size, and requires more subsequent treatments such as grinding and screening to optimize performance. In addition, more treatments are required to prevent or reduce agglomeration. The subsequent treatment is cumbersome and not suitable for the needs of large-scale industrial production.

[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; pipetting a certain volume of fluorescent substance solution and adding it 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 improperly 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 amount, 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 the problem to be solved by the present invention. Summary of the Invention

[0006] The present invention aims to address the shortcomings of existing technologies by providing a multi-color phosphor, its spray-drying preparation, and its application. To address these issues, the present invention proposes a spray-drying method for preparing a multi-color phosphor. This method features a simple synthesis, high reaction reproducibility, and scalable production. The phosphor produced by this method exhibits the excellent optical properties of typical fluorescent materials, achieving efficient solid-state luminescence while also paving the way for industrialized production.

[0007] The technical solution of the present invention is achieved as follows:

[0008] A spray drying method for preparing multi-color fluorescent powder comprises the following steps:

[0009] (1) Preparation of colorful carbon quantum dots;

[0010] (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;

[0011] (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;

[0012] (4) Preparation of multi-color phosphor: Set 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. The solid powder product is collected. The product is the multi-color phosphor.

[0013] In the spray-drying preparation method of a multi-color phosphor as described above, the multi-color carbon quantum dots in step (1) are selected from any one of blue carbon quantum dots, green carbon quantum dots, cyan carbon quantum dots, orange carbon quantum dots, and red carbon quantum dots.

[0014] In the above-mentioned spray-drying preparation method of a multi-color phosphor, in step (2), the absorbance of the multi-color carbon quantum dot solution is adjusted to 0.05-10 using a spectrophotometer.

[0015] In the spray-drying preparation method of the multi-color phosphor described above, in step (3), the carrier solution is an aqueous solution or an anhydrous ethanol solution of 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 dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, magnesium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, polyvinyl pyrrolidone, polyethylene glycol 10000, polyethylene glycol 20000, polyvinyl alcohol, and polyacrylic acid, or any two or more thereof.

[0016] In the above-mentioned spray drying method for preparing a multi-color phosphor, 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.

[0017] In the spray-drying preparation method of a multi-colored phosphor as described above, in step (3), the carrier solution is a saturated salt solution or a saturated salt solution containing polyethylene glycol; the volume ratio of the multi-colored 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).

[0018] In the spray-drying preparation method of the multi-color phosphor as described above, in step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

[0019] Based on the same inventive concept, the present invention provides a multi-colored phosphor prepared using the spray drying preparation method described above.

[0020] The multi-color 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.

[0021] Based on the same inventive concept, the present invention provides a method for preparing multi-colored phosphors as described above or an application of the multi-colored phosphors as described above, wherein the multi-colored phosphors are used to prepare display devices, laser lighting, LED lighting or luminous materials.

[0022] The beneficial effects of the present invention are:

[0023] 1. The spray-drying preparation method of a multi-color 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 protects the structure of the multi-color phosphor from high-temperature damage. In particular, it is easier to preserve the structure of the carrier itself for heat-sensitive components, which helps to improve the uniformity and optical properties of the multi-color phosphor.

[0024] 2. The spray drying preparation method of the multi-color phosphor 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.

[0025] 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. It can also maintain color consistency at different viewing angles and under long-term use, which is particularly important for applications requiring high color reproduction and long-term stability.

[0026] 4. The multi-color phosphors prepared by the spray-drying method of the present invention are environmentally friendly, low-cost, and readily available, and can be used to prepare display devices, laser lighting, LED lighting, or luminous materials. Blue LEDs (B-LEDs), green LEDs (G-LEDs), orange LEDs (O-LEDs), and red LEDs (R-LEDs) prepared using the multi-color phosphors of the present invention can produce bright blue, green, orange-red, and red light. White LEDs (WLEDs) prepared using the multi-color phosphors of the present invention emit light covering nearly the entire visible light range (400-720 nm), and when powered, they emit bright white light. This demonstrates the potential of the spray-drying method for preparing high-performance phosphors, creating conditions for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a scanning electron microscope image of the phosphor BCDs / NaCl-1 prepared in Comparative Example 1;

[0028] Figure 2 Scanning electron microscope images of the phosphor BCDs / NaCl-2 prepared in Example 1, wherein the scale bar in (A) is 1 μm and the scale bar in (B) is 5 μm;

[0029] Figure 3 Transmission electron micrographs of the phosphor BCDs / NaCl-2 prepared in Example 1 at different angles, wherein the scale bars in (A) and (B) are both 500 nm;

[0030] Figure 4 The following are Fourier transform infrared spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5;

[0031] Figure 5 This is a comparison chart of the X-ray diffraction spectra of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5;

[0032] Figure 6 (A) is a comparison chart of the fluorescence intensity and quantum yield of the blue phosphors prepared in Example 1, Example 7, and Comparative Example 1 at different outlet temperatures; Figure 6 (B) is a comparison of the fluorescence intensity and quantum yield of the blue phosphors 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;

[0033] Figure 7This is a comparison chart of the fluorescence intensities of the phosphor BCDs / NaCl-2 prepared in Example 1 and the phosphor BCDs powder prepared in Example 5;

[0034] Figure 8 The fluorescence spectrum of the blue phosphor BCDs / NaCl-2 prepared in Example 1;

[0035] Figure 9 This is a scanning electron microscope image of the yellow-green phosphor GCDs / PEG400 / NaCl-1 prepared in Comparative Example 3;

[0036] Figure 10 Scanning electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles, where the scale bars in (A) and (B) are both 5 μm, and the scale bar in (C) is 3 μm;

[0037] Figure 11 Transmission electron microscopy images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles. The scale bars in (A), (B), and (C) are all 500 nm.

[0038] Figure 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;

[0039] Figure 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;

[0040] Figure 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;

[0041] Figure 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;

[0042] Figure 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;

[0043] Figure 17 This is a comparison chart of the fluorescence intensities 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;

[0044] Figure 18 This is the fluorescence spectrum of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2;

[0045] Figure 19 This is a scanning electron microscope image of the orange phosphor OCDs / PEG400 / NaCl-1 prepared in Comparative Example 6;

[0046] Figure 20 Scanning electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles, where the scale bars in (A) and (B) are both 5 μm;

[0047] Figure 21 Transmission electron microscopy images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles, where the scale bars in (A) and (B) are both 500 nm;

[0048] Figure 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;

[0049] Figure 23 This is a comparison chart of the fluorescence intensities of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 and the phosphor OCDs / NaCl-2 prepared in Comparative Example 5;

[0050] Figure 24 This is the fluorescence spectrum of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3;

[0051] Figure 25 This is the fluorescence spectrum of the phosphor RCDs@PVP prepared in Example 4;

[0052] Figure 26Emission 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 photographs after power-on; (E) CIE coordinates of the B-LED, G-LED, O-LED, and R-LED; (F) emission spectra of the B-LED, (G) G-LED, (H) O-LED, and (I) R-LEDs;

[0053] Figure 27 Figure 3. 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. (A) CIE coordinates of the WLED, (B) emission spectrum of the WLED, and the inset is a photograph of the light emission of the WLED after power was applied. DETAILED DESCRIPTION

[0054] The following will be combined with the contents of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0055] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are intended solely for the purpose of describing specific embodiments and are not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0056] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0057] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0058] The present invention provides a spray-drying preparation method of multi-color phosphor, comprising the following steps:

[0059] A spray drying method for preparing multi-color fluorescent powder comprises the following steps:

[0060] (1) Preparation of colorful carbon quantum dots;

[0061] (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;

[0062] (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;

[0063] (4) Preparation of multi-color phosphor: Set 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. The mixed solution is atomized into small particles in a high-speed airflow, and then quickly dried to a solid powder product. The solid powder product is collected. The product is the multi-color phosphor.

[0064] 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.

[0065] The "carrier" in the present invention refers to a substance used to carry and disperse colorful carbon quantum dots, which enables uniform microparticles 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 dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, magnesium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, polyvinyl pyrrolidone, polyethylene glycol 10000, polyethylene glycol 20000, polyvinyl alcohol, polyacrylic acid, or any two or more aqueous solutions or anhydrous ethanol solutions.

[0066] 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. Corresponding process parameters are set through a spray drying device, and the colorful carbon quantum dots are embedded in the salt ion crystals, thereby increasing the particle distance between the colorful carbon quantum dots. In addition, the polyethylene glycol and the saturated salt solution work together to protect the luminescent centers of the colorful carbon quantum dots, thereby realizing the photoluminescence of the colorful carbon quantum dots in the solid state.

[0067] 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 also affect 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).

[0068] 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 these conditions, 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 can be improved, providing a direction for achieving industrial production.

[0069] 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.

[0070] 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.

[0071] 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%.

[0072] 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 caused by severe reaction conditions, greatly improves the yield of the phosphor, simplifies the preparation process of the phosphor; and creates conditions for industrial production. This method is simple to operate, has a high repetition rate, is low in 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 phosphor is the highest 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 phosphor is the highest and the quantum yield is close to the highest.

[0073] 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 striker speed is set to 2 s.

[0074] Preferably, in step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

[0075] Based on the same inventive concept, the present invention provides a multi-colored phosphor prepared using the spray drying preparation method described above.

[0076] The multi-color 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 multi-color 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.

[0077] Based on the same inventive concept, the present invention provides a multi-color phosphor prepared by the above-described preparation method or an application of the above-described multi-color phosphor, wherein the multi-color phosphor is used to prepare display devices, laser lighting, LED lighting, or luminous materials. Preferably, the multi-color phosphor is used to prepare LED lighting, such as blue LEDs, green LEDs, orange LEDs, red LEDs, and white LEDs.

[0078] 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, green, orange-red, and red light. Their emission wavelengths are located at 431 nm, 527 nm, 600 nm, 613 nm, and 657 nm, respectively.

[0079] Preferably, the LED lighting is a white light LED (WLED), in which the mass ratio of blue light phosphor, green light phosphor, orange light phosphor and red light phosphor is 2:2:1:1, the emission almost covers the entire visible light region (400~720 nm), and the LED device emits bright white light when powered on.

[0080] Example 1

[0081] 1. Preparation of Blue-Emitting Carbon Quantum Dots: Dissolve 0.08 g of phthalonitrile and 1.0 g of citric acid in 20.0 mL of 0.8 M sodium hydroxide solution. The solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and hydrothermally heated at 180°C for 8 h. After cooling naturally to room temperature, the pale yellow solution was neutralized with dilute hydrochloric acid and the pH was adjusted to 7, yielding a pale blue solution, which is the blue-emitting carbon quantum dots (B-CDs).

[0082] 2. Preparation of the blue phosphor (BCDs / NaCl-2) of this embodiment:

[0083] (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.

[0084] (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, which is a saturated sodium chloride solution.

[0085] (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, and 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 impactor 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. 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 the blue phosphor, which was named BCDs / NaCl-2.

[0086] The fluorescence quantum yield of the blue phosphor prepared in Example 1 of the present invention was tested using an Edinburgh fluorescence spectrometer FLS1000. The fluorescence quantum yield of the blue phosphor prepared in Example 1 of the present invention was 48.95%.

[0087] Example 2

[0088] 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. The solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and solvothermally heated at 200°C for 8 h. After cooling to room temperature, the solution was neutralized with a dilute hydrochloric acid solution of a certain concentration and the pH was adjusted to 7, yielding a green solution, referred to as green carbon quantum dots (G-CDs).

[0089] 2. Preparation of the green phosphor (GCDs / PEG400 / NaCl-2) of this embodiment:

[0090] (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.

[0091] (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.

[0092] (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, including the outlet temperature of the spray drying device at 100 °C, the fan speed at 90%, the peristaltic pump speed at 15%, and the impactor speed at 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 a magnetic stirrer. 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 the green phosphor, which was named GCDs / PEG400 / NaCl-2.

[0093] The measuring 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 results showed that the fluorescence quantum yield of the green phosphor prepared in Example 2 of the present invention was 49.23%.

[0094] Example 3

[0095] Preparation of Orange-Emitting Carbon Quantum Dots: Dissolve 1.0 mL of polyethylene glycol 400 and 30.0 mg of RhB in 15.0 mL of anhydrous ethanol. The RhB solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and solvothermally heated at 180°C for 8 h. After cooling to room temperature, an orange-red solution was obtained, representing the orange-emitting carbon quantum dots (O-CDs).

[0096] 2. Preparation of the orange phosphor (OCDs / PEG400 / NaCl-2) of this embodiment:

[0097] (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.

[0098] (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.

[0099] (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 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 impactor 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 a magnetic stirrer. 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 the orange phosphor, which was named OCDs / PEG400 / NaCl-2.

[0100] The measuring 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 results showed that the fluorescence quantum yield of the orange phosphor prepared in Example 3 of the present invention was 54.41%.

[0101] Example 4

[0102] 1. Preparation of Red-Emitting Carbon Quantum Dots: Weigh 0.108g of o-phenylenediamine and 0.346g of p-aminobenzenesulfonic acid in a mortar and grind for 3 minutes to thoroughly mix and form a fine powder. The ground powder was then transferred to a polytetrafluoroethylene-lined container and reacted in an electric forced-air drying oven at 200°C for 8 hours. After the reactor cooled to room temperature, a fluffy black powder was obtained. The black powder was washed three times with water (centrifuged at 10,000 rpm for three times, each for 5 minutes) to remove the generated acid. Finally, the powder was dried in a 60°C oven to obtain a black powder, which is the red-emitting carbon quantum dots (hereinafter referred to as R-CDs).

[0103] 2. Preparation of the red phosphor of this embodiment:

[0104] (1) Preparation of R-CDs solution: Weigh 5 mg of R-CDs powder and place it in 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.

[0105] (2) Preparation of red phosphor: Weigh 25 g of polyvinyl pyrrolidone (PVP) as a dispersant for carbon dots and add it to anhydrous ethanol containing RCDs. Stir until completely dissolved to 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 impactor 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 a magnetic stirrer. 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.

[0106] 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 results showed that the fluorescence quantum yield of the red phosphor prepared in Example 4 of the present invention was 20.28%.

[0107] Example 5

[0108] 1. Preparation of Blue-Emitting Carbon Quantum Dots: Dissolve 0.08 g of phthalonitrile and 1.0 g of citric acid in 20.0 mL of 0.8 M sodium hydroxide solution. The solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and hydrothermally heated at 180°C for 8 h. After cooling naturally to room temperature, the pale yellow solution was neutralized with dilute hydrochloric acid and the pH was adjusted to 7, yielding a pale blue solution, which is the blue-emitting carbon quantum dots (B-CDs).

[0109] 2. Preparation of blue phosphor powder (BCDs powder) of this embodiment:

[0110] (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.

[0111] (2) Preparation of blue phosphor: The BCDs solution was dialyzed for 8 h using a 1000 Da dialysis bag to obtain a dialyzed B-CDs solution. The parameters of the spray drying device were set, with the outlet temperature of the spray drying device set to 120 °C, the fan speed set to 90%, the peristaltic pump speed set to 15%, and the impactor speed set to 2 s. At the same time, the stirring rate of the dialyzed B-CDs solution was maintained at 900 rpm on a magnetic stirrer. 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 the blue phosphor, which was named BCDs powder.

[0112] The fluorescence quantum yield of the blue phosphor prepared in Example 5 of the present invention was tested using an Edinburgh fluorescence spectrometer FLS1000. The fluorescence quantum yield of the blue phosphor prepared in Example 5 of the present invention was 5.06%.

[0113] Example 6

[0114] 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. The solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and solvothermally heated at 200°C for 8 h. After cooling to room temperature, the solution was neutralized with a dilute hydrochloric acid solution of a certain concentration and the pH was adjusted to 7, yielding a green solution, referred to as green carbon quantum dots (G-CDs).

[0115] 2. Preparation of Green Phosphor (GCDs Powder) of This Example

[0116] (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.

[0117] (2) Preparation of green phosphor: The GCDs solution was dialyzed for 8 h using a 1000 Da dialysis bag to obtain a dialyzed G-CDs solution. The parameters of the spray drying device were set, with the outlet temperature of the spray drying device set to 120 °C, the fan speed set to 90%, the peristaltic pump speed set to 15%, and the impactor speed set to 2 s. At the same time, the stirring rate of the dialyzed G-CDs solution was maintained at 900 rpm on a magnetic stirrer. 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 the green phosphor, which was named GCDs powder.

[0118] The fluorescence quantum yield of the green phosphor prepared in Example 6 of the present invention was tested 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%.

[0119] Example 7

[0120] The same as Example 1, the only difference is that the outlet temperature of the spray drying device is changed to 80℃, 100℃, 150℃, and 180℃. The quantum yield and fluorescence intensity are tested using the determination method of Example 1. The results are as follows: Figure 6 As shown in A.

[0121] Example 8

[0122] 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.

[0123] Example 9

[0124] The same as Example 2, the only difference is that the outlet temperature of the spray drying device is changed to 80℃, 120℃, 150℃, and 200℃. The quantum yield and fluorescence intensity are tested using the determination method of Example 2. The results are as follows: Figure 14 shown.

[0125] Example 10

[0126] The same as Example 2, the only difference is 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. The results are as follows: Figure 15 shown.

[0127] Example 11

[0128] 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 method of Example 2. The results are as follows: Figure 16 shown.

[0129] Comparative Example 1:

[0130] 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. The power of the microwave oven is 700 W, the microwave operating frequency is 2450 MHz, the reaction time is 1.5 min, and the solution is taken out after cooling to room temperature and collected to obtain the phosphor. The phosphor prepared using this method is named BCDs / NaCl-1.

[0131] Comparative Example 2:

[0132] 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.

[0133] Comparative Example 3:

[0134] 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 using this method is named GCDs / PEG400 / NaCl-1.

[0135] Comparative Example 4:

[0136] The preparation method of the yellow-green phosphor in this comparative example is basically the same as that in 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.

[0137] Comparative Example 5:

[0138] 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.

[0139] Comparative Example 6:

[0140] 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 changed from 1:10 to 1:12; the content of PEG400 remains unchanged at 6%; the equipment is replaced by a microwave oven with a power of 700 W, a microwave operating frequency of 2450 MHz, a reaction time of 1.5 min, and the mixture is taken out after cooling to room temperature and collected to obtain the phosphor. The phosphor prepared using this method is named OCDs / PEG400 / NaCl-1.

[0141] Comparative Example 7:

[0142] The preparation method of the orange phosphor in this comparative example is basically the same as that in 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.

[0143] Application Example 1:

[0144] Blue light LED (B-LED), green light LED (G-LED), orange light LED (O-LED) and red light LED (R-LED) were prepared respectively using 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.

[0145] The phosphor BCDs / NaCl-2 prepared in this invention was used as a phosphor conversion layer to encapsulate blue LEDs. A dedicated LED chip with an emission peak of 365 nm was used as the excitation source to fabricate a blue LED light-emitting device. The encapsulation process was as follows: First, 0.2g of modified acrylate adhesive A and 0.2g of modified acrylate adhesive B were uniformly mixed with 0.1g of BCDs / NaCl-2 and applied evenly to a dedicated LED chip with an excitation wavelength of 365 nm. The adhesive was then cured at room temperature for 4 hours to produce a blue-emitting LED, designated B-LED. The device was then tested at a driving voltage of 3V. Modified acrylate adhesives A and B were purchased from Gelianghao New Materials Co., Ltd. in a boxed package of 80g AB (40g A + 40g B).

[0146] 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.

[0147] The preparation process and testing conditions of the O-LED prepared by the present invention are basically the same as those of the B-LED. The difference is that the blue light phosphor BCDs / NaCl-2 is replaced by the orange light phosphor OCDs / PEG400 / NaCl-2, and the dedicated LED chip with an emission peak of 365 nm is replaced by a dedicated LED chip with an emission peak of 490 nm.

[0148] 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 / NaCl-2 is replaced by the red light phosphor RCDs@PVP.

[0149] The test performance results are as follows Figure 26 shown.

[0150] Application Example 2:

[0151] 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.

[0152] 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 were adjusted and mixed with modified acrylate adhesive A and modified acrylate adhesive B to form 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. 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, they are coated on a dedicated LED chip with an excitation wavelength of 365nm, cured at room temperature for 4h, and a white light LED is obtained, recorded as WLED, and then relevant tests are carried out under the condition that the chip driving voltage is 3V. Among them, modified acrylic adhesive A and modified acrylic adhesive B were purchased from Gelianghao New Materials Co., Ltd., with the specifications being: AB80g (A40g+B40g) in a box.

[0153] The test performance results are as follows Figure 27 shown.

[0154] 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 figure that the morphology of the phosphor BCDs / NaCl-1 prepared by the microwave method presents a cubic structure, but the crystal structure is destroyed.

[0155] Figure 2 This is a scanning electron microscope image of the phosphor BCDs / NaCl-2 prepared in Example 1. Figure 2 A and Figure 2 As can be seen in B, the morphology of the phosphor prepared by spray drying is relatively regular. 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.

[0156] 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.

[0157] Figure 4 The following are Fourier transform infrared spectra of the BCDs / NaCl-2 phosphor prepared in Example 1 and the BCDs powder phosphor prepared in Example 5. As can be seen, the B-CDs exhibit absorption peaks at 1567 cm⁻¹, 3356 cm⁻¹, 1391 cm⁻¹, 1243 cm⁻¹, and 1057 cm⁻¹, corresponding to the stretching vibrations of C=N, -OH, -COO-, COC, and CO, respectively. A comparison reveals that the absorption bands of BCDs / NaCl-2 are consistent with those of BCDs, indicating that the surface groups of BCDs are preserved and undamaged after embedding into sodium chloride crystals. This also demonstrates that infrared light can transmit through sodium chloride crystals.

[0158] Figure 5 The following is a comparison of the X-ray diffraction spectra of the BCDs / NaCl-2 phosphor prepared in Example 1 and the BCDs powder prepared in Example 5. As can be seen from the figure, the diffraction peak position of the BCDs / NaCl-2 phosphor prepared in Example 1 corresponds almost exactly to that of a standard NaCl card. Furthermore, because the diffraction peak intensity of BCDs is weaker than that of NaCl crystals, the diffraction peak of BCDs is not reflected in the phosphor.

[0159] Figure 6 (A) is a comparison chart of the fluorescence intensity and quantum yield of the blue 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 phosphors 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 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 was found that when the volume ratio of BCDs solution (Abs = 0.5) to saturated sodium chloride solution was 1:1, as in Example 1, the fluorescence quantum yield and fluorescence intensity reached their maximum values, reaching 48.95% and 2616 (au), respectively. Comparison of the fluorescence properties of BCDs / NaCl blue phosphors prepared by microwave and spray drying methods revealed that the fluorescence intensity and fluorescence quantum yield of the blue phosphor BCDs / NaCl-2 prepared by the spray drying method in Example 1 were stronger and higher than those of the blue phosphor BCDs / NaCl-1 prepared by the microwave method. Therefore, the BCDs / NaCl-2 blue phosphor can be produced on a large scale.

[0160] Figure 7 This figure compares the fluorescence intensities of the BCDs / NaCl-2 phosphor prepared in Example 1 and the BCDs powder prepared in Example 5. The figure shows that the fluorescence intensity of the phosphor prepared in Example 5 is very weak, at 439 au, and its fluorescence quantum yield is also low, at 5.06%. When B-CDs is dispersed in a sodium chloride matrix, its fluorescence intensity increases significantly, reaching 2616 au, and its fluorescence quantum yield also increases to 48.95%.

[0161] Figure 8 This is the fluorescence spectrum of the blue phosphor BCDs / NaCl-2 prepared in Example 1. As can be seen from the figure, the optimal excitation wavelength of the blue phosphor BCDs / NaCl-2 is 360 nm, the emission peak is at 427 nm, and the spectrum retains the optical property of BCDs solution excitation independence.

[0162] Figure 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 reaction is too intense.

[0163] Figure 10 The scanning electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles are shown. Figure 10 A. Figure 10 B and Figure 10 C It can be seen that the morphology of the phosphor prepared by the spray drying method presents a regular cubic structure. This is because the reaction conditions of the spray drying method are relatively mild and it is easier to preserve the structure of the salt crystal itself.

[0164] Figure 11 Transmission electron microscope images of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 at different angles. Figure 11 A. Figure 11 B and Figure 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.

[0165] Figure 12 The X-ray diffraction spectra of the phosphor GCDs / PEG400 / NaCl-2 prepared in Example 2 and the phosphor G-CDspowder prepared in Example 6 show that the diffraction peak positions of GCDs / PEG400 / NaCl-2 prepared by spray drying method have 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.

[0166] Figure 13 The following are Fourier transform 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 during the formation of G-CDs / PEG400 / NaCl-2, the groups on the surface of GCDs are completely retained. For example, the characteristic peaks of representative -OH, C=N, C=C / CN, and O=CO can all be reflected in GCDs / PEG400 / NaCl-2.

[0167] Figure 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. Figure 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 reach the highest, thereby determining the feasibility of the spray drying method for preparing the phosphor.

[0168] Figure 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. Figure 15It can be seen 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.

[0169] Figure 16 The following is a comparison of the fluorescence intensity and quantum yield 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 the GCDs is adjusted to 1.25. Figure 16 As shown, under the same test conditions, it was measured that when the volume ratio of GCDs solution to saturated sodium chloride solution with a PEG400 content of 6% was 1:3, that is, Example 2, the fluorescence intensity and quantum yield reached the highest. It can be considered that the optimal volume ratio of GCDs solution to saturated sodium chloride solution with a PEG400 content of 6% is 1:3 for process production.

[0170] Figure 17 This is a fluorescence intensity comparison chart 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. It can be seen from the figure that the phosphor powder prepared directly 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%; the GCDs / NaCl-2 prepared in Comparative Example 2, when G-CDs are dispersed in a sodium chloride matrix, has a very weak fluorescence intensity of 73.9 (au) and a fluorescence quantum yield of 4.56%; however, in Example 2, when PEG400 is present at a content of 6% in the saturated sodium chloride solution, the fluorescence intensity of GCDs / PEG400 / NaCl-2 is greatly increased to 1743 (au), and the fluorescence quantum yield is 49.23%.

[0171] Figure 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 optimal excitation wavelength at 500nm and the emission peak position at 535nm.

[0172] Figure 19This 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 milder reaction conditions are needed to retain the crystal structure of sodium chloride.

[0173] Figure 20 The scanning electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles are shown. Figure 20 A and Figure 20 As can be seen in Figure B, the phosphor successfully prepared in this example exhibits a relatively regular and complete cubic structure of sodium chloride crystals and a smooth surface. This is mainly because during spray drying, the O-CDs and the saturated sodium chloride solution containing PEG400 are continuously stirred and then uniformly fed into the spray gun of the spray drying equipment through a peristaltic pump. The entire process is relatively gentle, thus causing minimal damage to the crystal morphology.

[0174] Figure 21 Transmission electron microscope images of the phosphor OCDs / PEG400 / NaCl-2 prepared in Example 3 at different angles. Figure 21 A and Figure 21 As can be seen in B, OCDs are evenly dispersed inside the sodium chloride crystals. It can be seen that PEG400 and OCDs form a stable structure by bonding and enter the interior of the sodium chloride crystals, thereby realizing solid-state luminescence.

[0175] Figure 22 This is a comparison 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. As can be seen from the figure, the XRD patterns of the two basically correspond to the main diffraction peaks in the NaCl standard card (JCPDS card number 99-0059). Therefore, the embedding of PEG400 and OCDs has no obvious effect on the crystallization properties of sodium chloride.

[0176] Figure 23This figure compares the fluorescence intensities of the OCDs / PEG400 / NaCl-2 phosphor prepared in Example 3 and the OCDs / NaCl-2 phosphor prepared in Comparative Example 5. As can be seen from the figure, the fluorescence intensity and quantum yield of the OCDs / NaCl-2 phosphor prepared in Comparative Example 5 are relatively low, at 124 (au) and 28.32%, respectively. However, the introduction of PEG400 significantly increases the fluorescence intensity and quantum yield of the OCDs / PEG400 / NaCl-2 phosphor prepared in Example 3 to 1278 (au) and 54.41%, respectively. This demonstrates the successful preparation of Example 3, achieving the large-scale production of long-wavelength emission phosphors.

[0177] Figure 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 optimal excitation at 560 nm and an emission peak at 602 nm. This enables the large-scale preparation of solid-state luminescent materials emitting in the long-wavelength region and promotes the development of carbon quantum dots in the long-wavelength solid-state luminescence region.

[0178] Figure 25 This is the fluorescence spectrum of the phosphor RCDs@PVP prepared in Example 4. It is prepared with PVP as the matrix and R-CDs as the fluorescent substance. It can be seen from the figure that this example successfully prepared a red light phosphor with high fluorescence intensity, with the optimal excitation wavelength at 560nm and the emission peak position at 603nm.

[0179] Figure 26 These are 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. Figure 26 A~ Figure 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. Figure 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). Figure 26 F~ Figure 26Figure 1 shows the emission spectra of B-LED, G-LED, O-LED, and R-LED at 3.0 V, with emission wavelengths located at 431 nm, 527 nm, 600 nm, 613 nm, and 657 nm, respectively.

[0180] Figure 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. Figure 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. Figure 27 A The CIE chromaticity coordinates of the prepared WLED are (0.30, 0.35), which is close to the CIE 1931 chromaticity coordinates of the standard WLED, and the color temperature is 6947 K; Figure 27 Figure B shows the fluorescence spectrum of WLED at 3V. It can be clearly seen that the emission of the prepared WLED almost covers the entire visible light region (400~720nm), and Figure 27 The inset of B shows that the LED device emits bright white light when powered on.

[0181] The spray-drying preparation method of the multi-color phosphor provided by the present invention is simple to operate, can be expanded in production, and can realize the large-scale preparation of the phosphor process; at the same time, the spray-drying preparation method of the multi-color 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.

[0182] 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 principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A spray drying method for preparing phosphor, characterized in that: The following steps are involved: (1) Preparation of carbon quantum dots: Phthalonitrile and citric acid were dissolved in sodium hydroxide solution. The solution was then transferred to a stainless steel autoclave lined with polytetrafluoroethylene and hydrothermally heated. After cooling naturally to room temperature, it was neutralized with dilute hydrochloric acid solution to obtain a light blue solution, which is the blue light carbon quantum dots. (2) Preparation of carbon quantum dot solution: Place carbon quantum dots in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of the carbon quantum dot solution to 0.05-10 to obtain a blue light carbon quantum dot solution; (3) mixing the blue light carbon quantum dot solution in step (2) and a saturated sodium chloride solution to obtain a mixed solution; (4) Preparation of phosphor: Set 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. The solid powder product is collected. The product is the blue light phosphor.

2. A spray drying method for preparing phosphor, characterized in that: The following steps are involved: (1) Preparation of carbon quantum dots: Phthalonitrile and resorcinol were dissolved in sodium hydroxide solution, and then transferred to a stainless steel autoclave lined with polytetrafluoroethylene for solvent thermal heating. After cooling naturally to room temperature, the solution was neutralized with dilute hydrochloric acid solution to obtain a green solution, which is green light carbon quantum dots. (2) Preparation of carbon quantum dot solution: Place carbon quantum dots in a beaker, add deionized water, and use a spectrophotometer to adjust the absorbance of the carbon quantum dot solution to 0.05-10 to obtain a green light carbon quantum dot solution; (3) mixing the green carbon quantum dot solution in step (2) with a saturated sodium chloride solution containing 6% PEG400 to obtain a mixed solution; (4) Preparation of phosphor: Set 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. The solid powder product is collected. The product is the green phosphor.

3. A spray drying method for preparing phosphor, characterized in that: The following steps are involved: (1) Preparation of carbon quantum dots: Polyethylene glycol 400 and RhB were dissolved in anhydrous ethanol. Subsequently, the RhB solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene for solvent thermal heating. After cooling naturally to room temperature, an orange-red solution was obtained, which is the orange-light carbon quantum dots. (2) Preparation of carbon quantum dot solution: Place carbon quantum dots in a beaker, add anhydrous ethanol, and use a spectrophotometer to adjust the absorbance of the carbon quantum dot solution to 0.05-10 to obtain an orange light carbon quantum dot solution; (3) mixing the orange light carbon quantum dot solution in step (2) and a saturated sodium chloride solution containing 6% PEG400 to obtain a mixed solution; (4) Preparation of phosphor: Set 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. The solid powder product is collected. The product is the orange phosphor.

4. A spray drying method for preparing phosphor, characterized in that: The following steps are involved: (1) Preparation of carbon quantum dots: Weigh o-phenylenediamine and p-aminobenzenesulfonic acid in a mortar and grind them until they are fully mixed and become fine powder. Then transfer the ground powder to a polytetrafluoroethylene liner and react in an electric blast drying oven. After the reactor cools to room temperature, fluffy black powder is obtained. The black powder is washed three times with water and finally dried in an oven to obtain a black powder, which is red light carbon quantum dots. (2) Preparation of carbon quantum dot solution: Place carbon quantum dots in a beaker, add anhydrous ethanol, and use a spectrophotometer to adjust the absorbance of the carbon quantum dot solution to 0.05-10 to obtain a red light carbon quantum dot solution; (3) Weighing polyvinyl pyrrolidone as a dispersant for carbon dots, adding it to the red light carbon quantum dot solution in step (2), stirring it to completely dissolve it, and obtaining a mixed solution; (4) Preparation of phosphor: Set 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. The solid powder product is collected. The product is the red phosphor.

5. The spray drying method for preparing phosphor according to any one of claims 1 to 4, 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 striker speed is set to 1s to 2s.

6. The spray drying method for preparing phosphor according to any one of claims 1 to 4, characterized in that: In the step (4), the stirring rate of the magnetic stirring is 800 rpm to 1000 rpm.

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