High-quantum-yield fluorescent powder with calcium carbonate coated carbon dots regulated and controlled by double templates as well as preparation method and application of high-quantum-yield fluorescent powder

Abstract

The invention belongs to the technical field of nano luminescent materials. The invention discloses a preparation method of high-quantum-yield fluorescent powder with calcium carbonate coated carbon dots regulated and controlled by double templates. The preparation method comprises the following steps: (1) preparing a carbon dot solution; (2) adding a template agent and anhydrous calcium chloride into the carbon dot solution to obtain a mixed solution A; (3) dissolving anhydrous sodium carbonate into ethylene glycol to obtain a mixed solution B; (4) slowly dropwise adding the mixed solution B into the mixed solution A while stirring, stirring, and aging at room temperature to obtain a composite product; and centrifuging the composite product, collecting the precipitate, washing and drying to obtain the high-quantum-yield fluorescent powder. The crystal form is accurately regulated and controlled through double templates, an adaptive purification strategy is adopted, the limitation of a single process is effectively overcome, the method can be widely applied to carbon dots with different surface properties, and the obtained composite material is high in solid-state fluorescence quantum yield and good in stability and has important application value in the fields of solid-state luminescence, fluorescent falsification prevention, biological imaging and the like.

Description

Technical Field

[0001] This invention relates to the field of nanoluminescent materials technology, and in particular to a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by dual templates, its preparation method, and its application. Background Technology

[0002] Carbon dots (CDs), as an emerging zero-dimensional carbon nanomaterial, have shown great application potential in fields such as bioimaging, photocatalysis, and light-emitting diodes (LEDs) due to their unique optical properties, excellent water solubility, low toxicity, and tunable fluorescence emission wavelengths. In particular, with the advancement of synthesis technology, high-quantum-yield carbon dots covering the entire spectrum from blue to red light can now be prepared through simple methods such as hydrothermal and solvothermal methods.

[0003] However, carbon dots face a serious problem of aggregation-induced quenching (ACQ) in practical applications, especially as solid-state light-emitting devices (such as WLED phosphors). In solution, carbon dots exhibit good dispersion and high fluorescence intensity; however, when dried into solid powder, the drastic reduction in inter-dot distance leads to strong π-π stacking interactions, resulting in increased nonradiative transitions and a sharp decrease in fluorescence quantum yield, sometimes even complete quenching. To address this issue, researchers typically disperse carbon dots in a solid matrix (such as polymers, silica, or salt crystals), utilizing the spatial isolation of the matrix to prevent aggregation quenching.

[0004] Among various matrix materials, polymer matrices suffer from poor thermal stability and are prone to aging and yellowing with long-term use; silica matrices have complex preparation processes, typically involving a sol-gel process, which is time-consuming and costly. In contrast, calcium carbonate (CaCO3) has advantages such as good biocompatibility, inexpensive and readily available raw materials, and environmental friendliness, making it an ideal solid-state carrier for carbon dots. However, existing calcium carbonate-coated carbon dot technologies still have the following significant drawbacks: First, crystal form control is difficult, and the matching with carbon dots is poor. Calcium carbonate mainly exists in three crystal forms: calcite, aragonite, and vasaterite. Among them, calcite is the most stable but has a dense structure, making it difficult to effectively load guest molecules; although aragonite has better thermodynamic stability than vasaterite, it usually forms needle-like or columnar crystals with poor morphological regularity and lack of porous structure, which is also not conducive to uniform loading and high-efficiency capture of carbon dots; vasaterite has a porous spherical structure and a large specific surface area, making it most suitable for adsorbing and coating carbon dots, but it is extremely unstable in aqueous systems and easily transforms into calcite through dissolution and recrystallization, causing the originally coated carbon dots to be squeezed out of the lattice, resulting in a significant reduction in loading efficiency. More importantly, carbon dots with different luminescence colors and prepared by different methods have significant differences in surface functional groups and surface states, which have drastically different inducing effects on calcium carbonate nucleation and crystal form transformation. Existing technologies often lack effective template control methods to stabilize the corresponding crystal phase according to the characteristics of carbon dots.

[0005] Secondly, there is a lack of post-processing techniques that balance crystal stability and luminescence efficiency. This is currently the biggest technical bottleneck in the preparation of full-spectrum solid-state carbon dot phosphors. How to remove reaction byproducts while simultaneously ensuring the stability of calcium carbonate crystals and the efficient retention of carbon dots remains a challenge, and there is currently no universal solution for different carbon dot characteristics.

[0006] Furthermore, Chinese patent CN202010499499.0, filed by the inventors, discloses a microwave preparation method for multi-colored phosphors. This method uses a saturated salt solution to disperse fluorescent substances and obtains solid phosphors through microwave reaction. Chinese patent CN202411217456.3 discloses a multi-colored phosphor and its spray-drying preparation method, which mixes a multi-colored carbon dot solution with a carrier solution and obtains solid phosphors through spray drying. Both of these preparation methods can yield solid phosphors with good color development and high yield. However, the microwave method has a fast heating rate, which may lead to localized overheating; spray drying also requires setting a specific outlet temperature. Both methods result in high temperatures affecting the carbon dots or phosphors. Moreover, the phosphors prepared by Chinese patents CN202010499499.0 and CN202411217456.3 have large particle sizes and their morphological uniformity needs improvement, which is not conducive to wider applications.

[0007] In summary, existing technologies lack a universal preparation strategy that can simultaneously achieve stable crystal form control and prevent guest molecule loss at room temperature and pressure. How to effectively control the crystal form of calcium carbonate while avoiding carbon point loss during post-processing, thereby obtaining a full-spectrum solid-state fluorescent material with high quantum yield and resistance to aggregation quenching, is a technical challenge that needs to be solved in this field. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by providing a high-quantum-yield phosphor for calcium carbonate-coated carbon dots regulated by a dual-template approach, along with its preparation method and applications. Based on the aforementioned problems, this invention provides a simple and low-cost method for preparing a high-quantum-yield phosphor for calcium carbonate-coated carbon dots regulated by a dual-template approach. This invention also provides a high-efficiency solid-state phosphor for calcium carbonate-coated carbon dots. This method, through dual-template synergistic induction and differentiated post-processing, can effectively regulate and obtain the target crystal form (such as porous aragonite) of the calcium carbonate shell according to the surface characteristics of different carbon dots, achieving efficient, uniform, and robust coating of carbon dots within the calcium carbonate shell. This invention maximizes the retention of the composite material's fluorescence performance through a purification strategy adapted to the surface polarities of different carbon dots, thus overcoming the limitation of existing technologies where a single process cannot be universally applied to various types of carbon dots. The phosphor prepared by this method possesses excellent optical properties of fluorescent materials, achieving not only efficient solid-state luminescence but also practical applications in manufacturing.

[0009] The technical solution of this invention is implemented as follows: A method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by a dual-template approach includes the following steps: (1) Preparation of carbon dot solution: Add carbon dots to ethylene glycol and adjust to a certain absorbance to obtain carbon dot solution; (2) Add a certain amount of template agent and anhydrous calcium chloride to the carbon dot solution in step (1) to obtain mixed solution A; (3) Dissolve anhydrous sodium carbonate in ethylene glycol to obtain mixed solution B; (4) Add the mixed solution B from step (3) slowly to the mixed solution A from step (2) while stirring. After the addition is complete, stir for a period of time to allow it to react fully. Then, age the reaction solution at room temperature to obtain the composite product. Centrifuge the composite product to collect the precipitate, wash the precipitate with a washing solvent, and dry it to obtain the high quantum yield phosphor.

[0010] In the preparation method of high quantum yield phosphor with calcium carbonate-coated carbon dots controlled by dual templates as described above, the carbon dots in step (1) are selected from any one of blue carbon dots, green carbon dots, and orange carbon dots.

[0011] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots by dual template regulation as described above, in step (1), the absorbance of the carbon dot solution is adjusted to 1.8 to 2.5.

[0012] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots controlled by dual template as described above, in step (2), the template agent is any one or two of polyethylene glycol 400, polyethylene glycol 2000, polyethylene glycol 10000, polyacrylic acid, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, and sodium oleate.

[0013] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots controlled by dual template as described above, in step (2), the template agent is a mixture of polyethylene glycol 2000 and sodium dodecyl sulfate; the amount of the template agent is 0-9% (w / v).

[0014] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots by dual template regulation as described above, in step (2), the mass ratio of polyethylene glycol 2000 and sodium dodecyl sulfate is (1:6) to (6:1).

[0015] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots controlled by dual template as described above, in step (3), the molar concentration of anhydrous sodium carbonate in ethylene glycol is 0.2-0.3M.

[0016] In the preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots controlled by dual template as described above, the volume ratio of mixed solution A and mixed solution B in step (4) is (2-3):1.

[0017] The method for preparing high quantum yield phosphors with calcium carbonate-coated carbon dots controlled by dual templates as described above, wherein the dropping rate in step (4) is 2-3 drops / minute, the stirring time is 2-3 hours, and the aging time is 12-24 hours.

[0018] The preparation method of high quantum yield phosphor of calcium carbonate-coated carbon dots with dual template regulation as described above, the centrifugation conditions in step (4) are 10,000 rpm for 5 min.

[0019] Based on the same inventive concept, this invention provides a phosphor prepared using the method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots controlled by dual templates as described in any one of claims 1 to 7.

[0020] The phosphor described above is a blue phosphor with an emission peak wavelength of 410-500nm in the excitation wavelength range of 305-400nm, or a green phosphor with an emission peak wavelength range of 520-550nm in the excitation wavelength range of 480-515nm, or an orange phosphor with an emission peak wavelength range of 570-600nm in the excitation wavelength range of 515-570nm.

[0021] Based on the same inventive concept, the present invention provides a phosphor prepared by the preparation method described above or an application of the phosphor described above, wherein the phosphor is used to prepare LED devices, display devices, laser lighting or luminescent materials.

[0022] The beneficial effects of this invention are: 1. This invention provides a method for preparing high quantum yield phosphors of calcium carbonate-coated carbon dots under dual-template regulation. The method is simple, low-cost, and environmentally friendly, and allows the carbon dots to maintain their fluorescence properties in solution while in a solid state. It effectively suppresses aggregation-induced quenching effects, and the prepared composite phosphor can achieve a fluorescence quantum yield of over 90%, reaching an ultra-high fluorescence quantum yield level. This lays the foundation for the wider application of carbon dot-based phosphors.

[0023] 2. This invention provides a method for preparing high-quantum-yield phosphors with calcium carbonate-coated carbon dots under dual-template regulation. It creatively employs a dual-template system composed of a polymeric steric stabilizer and anionic surfactant in ethylene glycol. This system, through a synergistic mechanism of "electrostatically induced nucleation" and "steric hindrance-controlled growth," not only promotes heterogeneous nucleation of calcium carbonate with carbon dots as the core, but more importantly, effectively slows down the phase transition from metastable aragonite to calcite. This allows for the acquisition of a target crystalline calcium carbonate shell based on the surface characteristics of the carbon dots (e.g., successfully obtaining structurally stable and morphologically regular porous aragonite for blue light carbon dots), providing an ideal loading space for the carbon dots. The dual-template-induced heterogeneous nucleation ensures that calcium carbonate grows directly on the carbon dot surface, achieving uniform and complete coating. The interaction between the functional groups on the carbon dot surface and the forming calcium carbonate lattice firmly confines the carbon dots within the shell, preventing them from easily detaching.

[0024] 3. This invention proposes and verifies a differentiated washing and purification strategy based on the surface polarity (hydrophilic or hydrophobic) of carbon dots. This method overcomes the limitations of traditional washing methods, which often result in carbon dot loss or accelerated phase transitions. For hydrophilic carbon dots, washing with organic solvents avoids dissolution and reduces disturbance to water molecules at the shell-core interface; for hydrophobic carbon dots, washing with water avoids the erosion of the hydrophobic interface by organic solvents. This strategy ensures that high-performance composite fluorescent materials can be obtained from carbon dots of different sources and with different surface properties, greatly expanding the application scope of this technology.

[0025] 4. The high quantum yield phosphor prepared by this invention has good luminescence properties. Blue LEDs (B-LEDs), green LEDs (G-LEDs), and orange LEDs (O-LEDs) prepared with this phosphor can produce bright blue, green, and orange light, respectively. White LEDs (WLEDs) prepared with the phosphor of this invention emit light that covers almost the entire visible light region (420~700 nm), and the WLED device emits bright white light when powered on. Attached Figure Description

[0026] Figure 1 A, Figure 1 B. Figure 1 C is a scanning electron microscope image of the blue phosphor prepared in Comparative Example 2, Example 1 and Comparative Example 1 with an addition amount of 5% (w / v); Figure 2 Transmission electron microscope images of the phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, where the scale bar of (A) is 500 nm and the scale bar of (B) is 100 nm. Figure 3 Fourier transform infrared spectra of B-CDs prepared in Example 1, phosphor B-CDs@CaCO3 / PEG / SDS, phosphor B-CDs@CaCO3 prepared in Comparative Example 2, and phosphor up-waterwashed after being added to Comparative Example 1 at a concentration of 5% (w / v). Figure 4 Comparison of X-ray diffraction spectra of B-CDs@CaCO3 / PEG / SDS prepared in Example 1, phosphor prepared by up-water wash with ultrapure water at an addition amount of 5% (w / v) in Comparative Example 1, and B-CDs@CaCO3 prepared in Comparative Example 2. Figure 5 A is a comparison graph of the fluorescence quantum yield of the blue phosphors prepared in Examples 1, 4, 1, and 2. Figure 5 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Examples 1, 5 and 3; Figure 6 The fluorescence spectrum of the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1 is shown. Figure 7 A, Figure 7 B. Figure 7 C are scanning electron microscope images of green phosphors prepared under different conditions with an addition amount of 7% (w / v) in Comparative Example 5, Example 2 and Comparative Example 4, respectively. Figure 8Transmission electron microscope images of the phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, where the scale bar of (A) is 500 nm and the scale bar of (B) is 200 nm. Figure 9 Fourier transform infrared spectra of G-CDs prepared in Example 2, phosphor G-CDs@CaCO3 / PEG / SDS, phosphor G-CDs@CaCO3 prepared in Comparative Example 5, and phosphor up-waterwash prepared in Comparative Example 4 with an addition amount of 7% (w / v) after washing with ultrapure water. Figure 10 X-ray diffraction spectra of G-CDs@CaCO3 / PEG / SDS prepared in Example 2, phosphor prepared by up-water wash with ultrapure water at an addition amount of 7% (w / v) in Comparative Example 4, and G-CDs@CaCO3 prepared in Comparative Example 5 are compared. Figure 11 A is a comparison graph of the fluorescence quantum yield of the green phosphors prepared in Examples 2, 6, 4, and 5. Figure 11 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Example 2, Example 7 and Comparative Example 6; Figure 12 The fluorescence spectrum of the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2 is shown. Figure 13 A, Figure 13 B. Figure 13 C are scanning electron microscope images of orange phosphors prepared under different conditions in Comparative Example 8, Example 3 and Comparative Example 10, respectively. Figure 14 Transmission electron microscope image of the phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3, scale bar is 100 nm; Figure 15 Fourier transform infrared spectra of O-CDs prepared in Example 3, phosphor O-CDs@CaCO3 / PEG / SDS, phosphor O-CDs@CaCO3 prepared in Comparative Example 8, and phosphor anhydrous ethanol wash prepared in Comparative Example 10. Figure 16 Comparison of X-ray diffraction spectra of O-CDs@CaCO3 / PEG / SDS prepared in Example 3, phosphor prepared by washing with anhydrous ethanol in Comparative Example 10, and O-CDs@CaCO3 prepared in Comparative Example 8. Figure 17A is a comparison graph of the fluorescence quantum yield of the orange phosphors prepared in Example 8, Comparative Example 7 and Comparative Example 8; Figure 17 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Example 3, Example 9 and Comparative Example 9; Figure 18 The fluorescence spectrum of the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3 is shown. Figure 19 A, Figure 19 B. Figure 19 C shows the emission spectra of blue LEDs (B-LEDs), green LEDs (G-LEDs), and orange LEDs (O-LEDs) prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3. The inset shows photographs of each LED after it is powered on. Figure 19 D represents the CIE coordinates of B-LED, G-LED, and O-LED; Figure 20 The optical properties of white LEDs (WLEDs) prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3 are shown. Among them, (A) is the emission spectrum of the WLED, and the inset is a photograph of the WLED after it is powered on; (B) is the CIE coordinate of the WLED. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is 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.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0030] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0031] A method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by a dual-template approach includes the following steps: (1) Preparation of carbon dot solution: Add carbon dots to ethylene glycol to obtain a mixed solution. Adjust the absorbance of the mixed solution of carbon dots and ethylene glycol to a certain absorbance by adjusting the ratio of carbon dots to ethylene glycol using a spectrophotometer, and then obtain the carbon dot solution. (2) Add a certain amount of template agent and anhydrous calcium chloride to the carbon dot solution in step (1) to obtain mixed solution A; (3) Dissolve anhydrous sodium carbonate in ethylene glycol to obtain mixed solution B; (4) Add the mixed solution B from step (3) slowly to the mixed solution A from step (2) while stirring. After the addition is complete, stir for a period of time to allow it to react fully. Then, age the reaction solution at room temperature to obtain the composite product. Centrifuge the composite product to collect the precipitate and wash the precipitate with a small amount of washing solvent multiple times. After drying, the high quantum yield phosphor is obtained.

[0032] Preferably, the carbon dots in step (1) are selected from any one of blue carbon dots, green carbon dots, and orange carbon dots.

[0033] Preferably, blue carbon dots are prepared by a hydrothermal method using citric acid and ethylenediamine; green carbon dots are prepared by a hydrothermal reaction of polyethylene glycol 400 and rhodamine B (hereinafter referred to as "RhB") under alkaline conditions; and orange carbon dots are prepared by a solvothermal reaction of polyethylene glycol 400 and rhodamine B in anhydrous ethanol.

[0034] Preferably, in step (1), the absorbance of the carbon dot solution is adjusted to 1.8 to 2.5 using a spectrophotometer.

[0035] Preferably, in step (2), the template agent is any one or two of polyethylene glycol 400, polyethylene glycol 2000, polyethylene glycol 10000, polyacrylic acid, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, and sodium oleate.

[0036] Preferably, in step (2), the template agent is a mixture of PEG2000 and sodium dodecyl sulfate; the amount of the template agent is 0-9% (w / v). PEG2000 and sodium dodecyl sulfate, as dual template agents, can fully disperse carbon dots and form a dense, complete coating layer for calcium carbonate, thereby effectively isolating carbon dots, reducing aggregation-induced quenching, suppressing nonradiative relaxation of the external environment, and improving fluorescence quantum yield. However, when the template agent is excessive (greater than 9% (w / v)), excessive adsorption of the template agent will interfere with the orderly growth of calcium carbonate crystals, leading to increased defects in the coating layer and a loose structure, causing calcium carbonate to fail to uniformly coat carbon dots and reducing the fluorescence quantum yield of the material.

[0037] In some preferred embodiments of the present invention, carbon dots are added to an ethylene glycol solution containing polyethylene glycol 2000, sodium dodecyl sulfate, and calcium chloride and mixed thoroughly. Calcium carbonate is then generated by dropwise addition of an ethylene glycol solution containing sodium carbonate to this mixed solution. During the slow formation of calcium carbonate, the carbon dots are encapsulated within the calcium carbonate crystals, increasing the interparticle distance between the carbon dots. Furthermore, polyethylene glycol 2000 and sodium dodecyl sulfate can adjust the morphology of the calcium carbonate and modify the surface functional groups of the carbon dots, thereby achieving the fluorescent properties of the carbon dots in the solid state.

[0038] Preferably, in step (2), the mass ratio of polyethylene glycol 2000 to sodium dodecyl sulfate is (1:6) to (6:1).

[0039] In some preferred embodiments of the present invention, the amount of polyethylene glycol 2000 and sodium dodecyl sulfate added to the ethylene glycol solution containing B-CDs solution (A=1.8) and anhydrous calcium chloride is 5% (w / v), and the mass ratio of polyethylene glycol 2000 to sodium dodecyl sulfate is 1:1, resulting in the highest quantum yield of the generated blue phosphor.

[0040] In some preferred embodiments of the present invention, the amount of polyethylene glycol 2000 and sodium dodecyl sulfate added to the ethylene glycol solution containing G-CDs solution (A=2) and anhydrous calcium chloride is 7% (w / v), and the mass ratio of polyethylene glycol 2000 to sodium dodecyl sulfate is 1:1, resulting in the highest quantum yield of the generated green phosphor.

[0041] In some preferred embodiments of the present invention, the amount of polyethylene glycol 2000 and sodium dodecyl sulfate added to the ethylene glycol solution containing O-CDs solution (A=2.5) and anhydrous calcium chloride is 5% (w / v), and the mass ratio of polyethylene glycol 2000 to sodium dodecyl sulfate is 2:3, resulting in the highest quantum yield of the generated orange phosphor.

[0042] Preferably, in step (2), the concentration of anhydrous calcium chloride is 0.1M.

[0043] Preferably, in step (3), the molar concentration of anhydrous sodium carbonate in ethylene glycol is 0.2–0.3 M. Preferably, in step (3), the molar concentration of anhydrous sodium carbonate in ethylene glycol is 0.2 M.

[0044] Preferably, the volume ratio of mixed solution A and mixed solution B in step (4) is (2-3):1.

[0045] Preferably, in step (4), the dropping rate is 2-3 drops / minute, the stirring time is 2-3 hours, and the aging time is 12-24 hours. Through aging, the coating layer formed by calcium carbonate tends to be thermodynamically stable, obtaining a better interface state and avoiding the loss of carbon dots during subsequent washing.

[0046] Preferably, the centrifugation conditions in step (4) are 10,000 rpm for 5 min.

[0047] Preferably, the washing solvent in step (4) is anhydrous ethanol or ultrapure water. This invention proposes and verifies a differentiated washing and purification strategy based on the surface polarity (hydrophilic or hydrophobic) of carbon dots. For some hydrophilic carbon dots, if water is used to wash the CDs@CaCO3 complex, it is easy to induce a phase transition of metastable aragonite into calcite, causing the carbon dots to be expelled from the lattice; while for some alcoholic carbon dots, if ethanol is used for washing, the loaded carbon dots may be redissolved and lost due to the principle of "like dissolves like". However, the post-processing washing method of this application breaks through the limitations of traditional washing methods that lead to carbon dot loss or intensified phase transition. For hydrophilic carbon dots, washing with organic solvents can avoid their dissolution and reduce the disturbance of water molecules at the shell-core interface; for hydrophobic carbon dots, washing with water can avoid the erosion of the hydrophobic interface by organic solvents. This strategy ensures that carbon dots from different sources and with different surface properties can obtain high-performance composite fluorescent materials through this method, greatly expanding the application scope of this technology. In this invention, blue and green phosphors are obtained by washing and precipitating with anhydrous ethanol, while orange phosphor is obtained by washing and precipitating with ultrapure water. Test results show that the fluorescence quantum yield of the blue and green phosphors obtained by washing and drying with anhydrous ethanol is significantly higher than that of the phosphors obtained by washing and drying with ultrapure water. Similarly, the fluorescence quantum yield of the orange phosphor obtained by washing and drying with ultrapure water is significantly higher than that obtained by washing and drying with anhydrous ethanol.

[0048] In some preferred embodiments of the present invention, the fluorescence quantum yield of blue phosphor and green phosphor is maximized by washing with anhydrous ethanol, and the fluorescence quantum yield of orange phosphor is maximized by washing with ultrapure water.

[0049] Preferably, in step (4), the drying temperature is 60°C and the drying time is 12h.

[0050] Based on the same inventive concept, this invention provides a phosphor prepared using the high quantum yield phosphor preparation method for calcium carbonate-coated carbon dots controlled by a dual-template approach as described above. Existing technologies mostly employ cubic crystal structures. In solid-state luminescence applications, cubic crystal structures exhibit anisotropy, leading to uneven scattering and the tendency for defects to form at the edges, easily becoming quenching centers, thus affecting optical properties and hindering widespread application. In contrast, the phosphor prepared using the high quantum yield phosphor preparation method for calcium carbonate-coated carbon dots controlled by a dual-template approach as described in this application exhibits a regular spherical morphology, uniform light scattering, excellent luminescence performance, high structural stability, and ideal coating effect, facilitating processing and application.

[0051] Preferably, the phosphor is a blue phosphor with an emission peak wavelength of 410-500nm within the excitation wavelength range of 305-400nm, or a green phosphor with an emission peak wavelength range of 520-550nm within the excitation wavelength range of 480-515nm, or an orange phosphor with an emission peak wavelength range of 570-600nm within the excitation wavelength range of 515-570nm. More preferably, the phosphor is a blue phosphor with an emission peak wavelength of 437nm at an excitation wavelength of 360nm, or a green phosphor with an emission peak wavelength of 525nm at an excitation wavelength of 503nm, or an orange phosphor with an emission peak wavelength of 587nm at an excitation wavelength of 560nm.

[0052] Based on the same inventive concept, this invention provides a phosphor prepared by the method described above, or an application of the phosphor described above, wherein the phosphor is used to prepare LED devices, display devices, laser lighting, or luminescent materials. Preferably, the phosphor is used to prepare LED lighting, such as blue LEDs, green LEDs, orange LEDs, and white LEDs.

[0053] The blue LED (B-LED), green LED (G-LED), and orange LED (O-LED) prepared by this invention can produce bright blue, green, and orange light, respectively. Their emission wavelengths are located at 455 nm, 518 nm, and 607 nm, respectively.

[0054] Preferably, the LED lighting is a white LED (WLED), wherein the mass ratio of blue phosphor, green phosphor and orange phosphor is 1:7:2, the emission covers the entire visible light region (420~700 nm), and the LED device emits bright white light when powered on.

[0055] Example 1 1. Preparation of Blue Carbon Dots: 1 mmol of citric acid and 9 mmol of ethylenediamine were dissolved in 10 mL of ultrapure water and sonicated for approximately 10 min. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and hydrothermally reacted at 180°C for 6 h. The autoclave was then allowed to cool naturally to room temperature. The resulting product solution was filtered through a 0.45 μm microporous filter to obtain transparent liquid blue carbon dots, abbreviated as B-CDs. These were stored at 4°C for later use.

[0056] 2. Preparation of blue phosphor (B-CDs@CaCO3 / PEG / SDS) in this embodiment: (1) Preparation of B-CDs solution: Add 200 μL of B-CDs to 10 mL of ethylene glycol. Adjust the absorbance of the mixed solution of B-CDs and ethylene glycol to 1.8 using a spectrophotometer by adjusting the ratio of B-CDs to ethylene glycol. The desired B-CDs solution is then obtained.

[0057] (2) Take 10 mL of B-CDs solution and add 5% (w / v) of polyethylene glycol 2000 (hereinafter referred to as "PEG2000") and sodium dodecyl sulfate (hereinafter referred to as "SDS") to the solution. The mass ratio of PEG2000 to SDS is 1:1, that is, 0.25 g of each is added. Sonicate until completely dissolved. Then add 0.111 g of anhydrous CaCl2 and sonicate until completely dissolved to obtain mixed solution A.

[0058] (3) Dissolve 0.106g of anhydrous Na2CO3 completely in 5mL of ethylene glycol to obtain mixed solution B.

[0059] (4) Preparation of blue phosphor: Mixed solution B was slowly added to mixed solution A at a rate of 2-3 drops / min under vigorous stirring. After the addition was completed, the mixture was stirred for 2 hours to allow for a complete reaction. The reaction solution was then aged at room temperature for 12 hours to obtain the composite product. The composite product was collected by centrifugation (10,000 rpm, 5 min), and the precipitate was washed twice with 6 mL of anhydrous ethanol. After drying at 60 °C for 12 hours, the blue phosphor was obtained and named B-CDs@CaCO3 / PEG / SDS.

[0060] The fluorescence quantum yields of the liquid B-CDs and blue phosphor prepared in Example 1 of this invention were 70.4% and 94.28%, respectively, as measured by a FLS1000 fluorescence spectrometer from Edinburgh Instruments Ltd., UK.

[0061] Example 2 1. Preparation of green carbon dots: 1.0 mL of PEG400 and 30.0 mg of RhB were mixed in 15.0 mL of 0.67 M NaOH solution and sonicated until completely dissolved. The mixture was then subjected to hydrothermal reaction at 180°C for 8 h in a 25 mL stainless steel autoclave with a polytetrafluoroethylene liner. Afterward, the autoclave was allowed to cool naturally to room temperature, and large particles were removed by filtration through a 0.45 μm filter membrane, yielding clear and transparent liquid green carbon dots, denoted as G-CDs, which were stored at 4°C for later use.

[0062] 2. Preparation of the green phosphor (G-CDs@CaCO3 / PEG / SDS) in this embodiment: (1) Preparation of G-CDs solution: Add 200 μL of G-CDs to 10 mL of ethylene glycol. Adjust the absorbance of the mixed solution of G-CDs and ethylene glycol to 2 using a spectrophotometer by adjusting the ratio of G-CDs to ethylene glycol. The desired G-CDs solution is then obtained.

[0063] (2) Take 10 mL of LG-CDs solution and add 7% (w / v) of PEG2000 and SDS to the solution, wherein the mass ratio of PEG2000 and SDS is 1:1, that is, 0.35 g of each is added, and sonicated until completely dissolved. Then add 0.111 g of anhydrous CaCl2 and sonicate until completely dissolved to obtain mixed solution A.

[0064] (3) Dissolve 0.106g of anhydrous Na2CO3 completely in 5mL of ethylene glycol to obtain mixed solution B.

[0065] (4) Preparation of green phosphor: Mixed solution B was slowly added to mixed solution A at a rate of 2-3 drops / min under vigorous stirring. After the addition was completed, the mixture was stirred for 2 hours to allow for a complete reaction. The reaction solution was then aged at room temperature for 12 hours to obtain the composite product. The composite product was collected by centrifugation (10,000 rpm, 5 min), and the precipitate was washed twice with 6 mL of anhydrous ethanol. After drying at 60 °C for 12 hours, the green phosphor was obtained and named G-CDs@CaCO3 / PEG / SDS.

[0066] Using the determination method of Example 1, the fluorescence quantum yields of the liquid G-CDs and green phosphor prepared in Example 2 of this invention were 94.87% and 97.29%, respectively.

[0067] Example 3 1. Preparation of Orange Carbon Dots: 1.0 mL of polyethylene glycol 400 and 30.0 mg of RhB were dissolved in 15.0 mL of anhydrous ethanol and sonicated until completely dissolved. The mixture was then transferred to a 25 mL stainless steel autoclave lined with polytetrafluoroethylene and reacted solvothermically at 180°C for 8 hours. The autoclave was then allowed to cool naturally to room temperature. Large particles were removed by filtration through a 0.45 μm filter membrane to obtain liquid orange carbon dots, hereinafter referred to as O-CDs. These were stored at 4°C for later use.

[0068] 2. Preparation of orange phosphor (O-CDs@CaCO3 / PEG / SDS) in this embodiment: (1) Preparation of O-CDs solution: Add 200 μL of O-CDs to 10 mL of ethylene glycol. Adjust the absorbance of the O-CDs and ethylene glycol mixture to 2.5 using a spectrophotometer by adjusting the ratio of O-CDs to ethylene glycol. The desired O-CDs solution is then obtained.

[0069] (2) Take 10 mL of O-CDs solution and add 5% (w / v) of PEG2000 and SDS to the solution, wherein the mass ratio of PEG2000 to SDS is 2:3, that is, add 0.2 g and 0.3 g respectively, and sonicate until completely dissolved. Then add 0.111 g of anhydrous CaCl2 and sonicate until completely dissolved to obtain mixed solution A.

[0070] (3) Dissolve 0.106g of anhydrous Na2CO3 completely in 5mL of ethylene glycol to obtain mixed solution B.

[0071] (4) Preparation of orange phosphor: Mixed solution B was slowly added to mixed solution A at a rate of 2-3 drops / min under vigorous stirring. After the addition was completed, the mixture was stirred for 2 hours to allow for a complete reaction. The reaction solution was then aged at room temperature for 12 hours to obtain the composite product. The composite product was collected by centrifugation (10,000 rpm, 5 min), and the precipitate was washed twice with 6 mL of ultrapure water. After drying at 60 °C for 12 hours, the orange phosphor was obtained and named O-CDs@CaCO3 / PEG / SDS.

[0072] Using the determination method of Example 1, the fluorescence quantum yields of the liquid O-CDs and orange phosphor prepared in Example 3 of this invention were 64.43% and 91.04%, respectively.

[0073] Example 4 The results were essentially the same as in Example 1, except that the total amounts of PEG2000 and SDS added (mass ratio 1:1) were changed to 1%, 3%, 7%, and 9%. The quantum yield was tested using the method described in Example 1, and the results are as follows: Figure 5 As shown in Figure A.

[0074] Example 5 The results were essentially the same as in Example 1, except that the mass ratio of PEG2000 to SDS was changed to 1:4, 2:3, 3:2, and 4:1. The quantum yield was tested using the method described in Example 1, and the results are as follows: Figure 5 As shown in B.

[0075] Example 6 The results were essentially the same as in Example 2, except that the total amounts of PEG2000 and SDS added (mass ratio 1:1) were changed to 1%, 3%, 5%, and 9%. The quantum yield was tested using the method described in Example 2, and the results are as follows: Figure 11 As shown in Figure A.

[0076] Example 7 The results were essentially the same as in Example 2, except that the mass ratio of PEG2000 to SDS was 1:6, 2:5, 3:4, 4:3, 5:2, and 6:1. The quantum yield was tested using the method described in Example 2, and the results are as follows: Figure 11 As shown in B.

[0077] Example 8 The results were essentially the same as in Example 3, except that the total amounts of PEG2000 and SDS added (mass ratio 1:1) were changed to 1%, 3%, 5%, 7%, and 9%. The quantum yield was tested using the method described in Example 3, and the results are as follows: Figure 17 As shown in Figure A.

[0078] Example 9 The results were essentially the same as in Example 3, except that the mass ratio of PEG2000 to SDS was 1:4, 1:1, 3:2, and 4:1. The quantum yield was tested using the method described in Example 3, and the results are as follows: Figure 17 As shown in B.

[0079] Comparative Example 1: The preparation method of the blue phosphor used in this comparative example is basically the same as that in Example 4, except that in step (2), the total amount of PEG2000 and SDS added (mass ratio of 1:1) is 0%, 1%, 3%, 5%, 7%, and 9%, respectively. In step (4), the precipitate is washed with ultrapure water after centrifugation. The quantum yield was tested using the determination method of Example 1, and the results are as follows. Figure 5 As shown in Figure A.

[0080] Comparative Example 2: The preparation method of the blue phosphor used in this comparative example is basically the same as that in Example 1, except that PEG2000 and SDS were not added to the mixed solution A in step (2). The resulting product is denoted as B-CDs@CaCO3. Its quantum yield was tested using the method of Example 1, and the results are as follows. Figure 5 As shown in Figure A.

[0081] Comparative Example 3: The preparation method of the blue phosphor used in this comparative example is basically the same as that in Example 5, except that in step (2), the simultaneous addition of PEG2000 and SDS is changed to the addition of only 0.5 g of PEG2000 or only 0.5 g of SDS. The quantum yield was tested using the method described in Example 1, and the results are as follows: Figure 5 As shown in B.

[0082] Comparative Example 4: The preparation method of the green phosphor used in this comparative example is basically the same as that in Example 6, except that in step (2), the total amount of PEG2000 and SDS added (mass ratio of 1:1) is 0%, 1%, 3%, 5%, 7%, and 9%, respectively. In step (4), the precipitate is washed with ultrapure water after centrifugation. The quantum yield was tested using the method of Example 2, and the results are as follows. Figure 11 As shown in Figure A.

[0083] Comparative Example 5: The preparation method of the green phosphor used in this comparative example is basically the same as that in Example 2, except that PEG2000 and SDS were not added to the mixed solution A in step (2). The resulting product is denoted as G-CDs@CaCO3. Its quantum yield was tested using the method of Example 2, and the results are as follows. Figure 11 As shown in Figure A.

[0084] Comparative Example 6: The preparation method of the green phosphor used in this comparative example is basically the same as that in Example 7, except that in step (2), the simultaneous addition of PEG2000 and SDS is changed to the addition of only 0.7 g of PEG2000 or only 0.7 g of SDS. The quantum yield was tested using the method of Example 7, and the results are as follows: Figure 11 As shown in B.

[0085] Comparative Example 7: The preparation method of the orange phosphor used in this comparative example is basically the same as that in Example 8, except that in step (2), the total amount of PEG2000 and SDS added (mass ratio of 1:1) is 0%, 1%, 3%, 5%, 7%, and 9%, respectively. In step (4), the precipitate is washed with anhydrous ethanol after centrifugation. The quantum yield was tested using the determination method of Example 8, and the results are as follows. Figure 17 As shown in Figure A.

[0086] Comparative Example 8: The preparation method of the orange phosphor used in this comparative example is basically the same as that in Example 3, except that PEG2000 and SDS were not added to the mixed solution A in step (2) of the preparation of the orange phosphor. The resulting product is denoted as O-CDs@CaCO3. Its quantum yield was tested using the determination method of Example 3, and the results are as follows. Figure 17 As shown in Figure A.

[0087] Comparative Example 9: The preparation method for the orange phosphor used in this comparative example is basically the same as that in Example 9, except that the simultaneous addition of PEG2000 and SDS is changed to adding only 0.5 g of PEG2000 or only 0.5 g of SDS. The quantum yield was tested using the method of Example 9, and the results are as follows: Figure 17 As shown in B.

[0088] Comparative Example 10: The preparation method of the orange phosphor used in this comparative example is basically the same as that in Example 3. The difference is that in step (4), the precipitate is washed with anhydrous ethanol after centrifugation.

[0089] Application Example 1: Blue LEDs (B-LEDs), green LEDs (G-LEDs), and orange LEDs (O-LEDs) were prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3, respectively.

[0090] The phosphor B-CDs@CaCO3 / PEG / SDS prepared in this invention is used as the fluorescence conversion layer for encapsulating blue LEDs. A dedicated LED chip with an emission peak of 365-370nm is selected as the excitation source to fabricate blue LED light-emitting devices. The encapsulation process is as follows: First, 0.1g of B-CDs@CaCO3 / PEG / SDS is mixed with 50μL of high-transparency epoxy resin component B. After stirring evenly, high-transparency epoxy resin component A (volume ratio of 2.5:1 to component B) is added and mixed evenly. This mixture is then coated onto the dedicated LED chip with an excitation wavelength of 365-370nm. The mixture is then cured in a 60℃ oven for 6 hours to obtain a blue-emitting LED, denoted as B-LED. Relevant tests are then conducted under a chip driving voltage of 3V. The high-transparency epoxy resins A and B were purchased from Dongguan Guangzhan Adhesive Industry Co., Ltd., with specifications of 750g and 250g bottles, respectively.

[0091] The preparation process and testing conditions of the G-LED prepared by this invention are basically the same as those of the B-LED. The difference is that the blue phosphor B-CDs@CaCO3 / PEG / SDS is replaced with the green phosphor G-CDs@CaCO3 / PEG / SDS.

[0092] The preparation process and testing conditions of the O-LED prepared by this invention are basically the same as those of the B-LED. The difference is that the blue phosphor B-CDs@CaCO3 / PEG / SDS is replaced with the orange phosphor O-CDs@CaCO3 / PEG / SDS.

[0093] Its test performance results are as follows Figure 19 As shown.

[0094] Application Example 2: White LEDs (WLEDs) were prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3, wherein the mass ratio of B-CDs@CaCO3 / PEG / SDS, G-CDs@CaCO3 / PEG / SDS, and O-CDs@CaCO3 / PEG / SDS was 1:7:2.

[0095] The mass ratios of the blue phosphor B-CDs@CaCO3 / PEG / SDS, the green phosphor G-CDs@CaCO3 / PEG / SDS, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in this invention are adjusted, and then mixed with high-transparency epoxy resin adhesive A and high-transparency epoxy resin adhesive B to form the fluorescence conversion layer of WLED. The specific operation is as follows: B-CDs@CaCO3 / PEG / SDS, G-CDs@CaCO3 / PEG / SDS, and O-CDs@CaCO3 / PEG / SDS are mixed uniformly at a mass ratio of 1:7:2. This mixture is then added to 50 μL of high-transparency epoxy resin component B and stirred until homogeneous. Next, high-transparency epoxy resin component A (volume ratio of 2.5:1 to component B) is added and mixed thoroughly. Specifically, the mass of B-CDs@CaCO3 / PEG / SDS is 0.01 g, G-CDs@CaCO3 / PEG / SDS is 0.07 g, and O-CDs@CaCO3 / PEG / SDS is 0.02 g. This mixture is then coated onto an LED-specific chip with an excitation wavelength of 365-370 nm and cured in a 60℃ oven for 6 hours to obtain a white LED, denoted as WLED. Relevant tests are then conducted under a chip driving voltage of 3V. Among them, the high-transparency epoxy resin adhesive A and the high-transparency epoxy resin adhesive B were purchased from Dongguan Guangzhan Adhesive Industry Co., Ltd., and their specifications are 750g and 250g in bottles, respectively.

[0096] Its test performance results are as follows Figure 20 As shown.

[0097] Figure 1 A, Figure 1 B. Figure 1 C represents scanning electron microscope images of blue phosphors prepared under different conditions using 5% (w / v) addition to Comparative Example 2, Example 1, and Comparative Example 1, respectively. Figure 1 As can be seen from Figure A, the phosphor morphology prepared without the addition of template agents PEG2000 and SDS exhibits obvious aggregation; from Figure 1 As can be seen from B, the B-CDs@CaCO3 / PEG / SDS phosphor prepared according to Example 1 exhibits a more uniform aggregate morphology; from Figure 1 As can be seen in C, the phosphor obtained by washing with ultrapure water exhibits a more obvious spherical morphology, but it can be seen that its crystal structure is destroyed, which is not conducive to the coating of carbon dots. Figure 2 Transmission electron microscopy image of the phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1. From... Figure 2 A and Figure 2As can be seen from B, B-CDs@CaCO3 / PEG / SDS is composed of many spherical nanoparticles aggregated together, and B-CDs are uniformly distributed on these nanosheets.

[0098] Figure 3 Fourier transform infrared (FTIR) spectra of B-CDs prepared in Example 1, phosphor B-CDs@CaCO3 / PEG / SDS, phosphor B-CDs@CaCO3 prepared in Comparative Example 2, and phosphor prepared in Comparative Example 1 at 5% (w / v) after up-water washing with ultrapure water. The figures show that the absorption peaks of B-CDs are due to the stretching vibrations of OH / NH, C=O, CN, and CO. The peak of B-CDs@CaCO3 / PEG / SDS is at 3366 cm⁻¹. - The absorption peak at ¹ is attributed to the -OH stretching vibration of hydroxyl groups on the surface of B-CDs and the terminal hydroxyl groups of PEG2000; 2940 cm⁻¹ - ¹ and 2882 cm - ¹ Corresponding to the asymmetric and symmetric stretching vibrations of -CH2- in the alkyl chains of PEG2000 and SDS, respectively, the successful composite of the organic components was confirmed. 1433 cm - ¹ and its acromion 1485 cm - ¹、875 cm - ¹ and 743 cm - ¹ represents CO3 in CaCO3 2- The characteristic absorption peaks, corresponding sequentially to in-plane bending, out-of-plane bending, and lattice vibrations, indicate that CaCO3 is the main crystal form of this composite material; 1345 cm⁻¹ - ¹ represents the superposition peak of the -CH2- rocking vibration and the CO stretching vibration of the B-CDs surface. 1087 cm⁻¹ - ¹ is the characteristic stretching vibration peak of the COC bond in PEG2000 polyether, at 1044 cm⁻¹. - ¹The S=O stretching vibration of the sulfate anion in SDS contributes to this. These characteristic peaks confirm the successful preparation of the B-CDs@CaCO3 / PEG / SDS composite. Up-water washing of the material in Comparative Example 1 with a 5% (w / v) addition and washed with ultrapure water shows that washing with ultrapure water increases the functional groups on the surface of the composite material and shifts the position of the calcium carbonate characteristic peak, indicating that the crystal structure of calcium carbonate is disrupted.

[0099] Figure 4Comparison of X-ray diffraction spectra of B-CDs@CaCO3 / PEG / SDS prepared in Example 1, up-water wash phosphor prepared in Comparative Example 1 with 5% (w / v) addition and washed with ultrapure water, and B-CDs@CaCO3 prepared in Comparative Example 2. The figures show that the diffraction peak positions of the phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1 correspond almost completely to the standard cards of the corresponding aragonite-type CaCO3; the diffraction peaks of the up-waterwash composite material obtained by ultrapure water washing correspond almost completely to the standard cards of calcite-type CaCO3; while the diffraction peaks of B-CDs@CaCO3 include both the standard peaks of aragonite-type CaCO3 and calcite-type CaCO3. These results indicate that the addition of template agents PEG2000 and SDS helps CaCO3 maintain its metastable crystal form, while washing with ultrapure water accelerates the transformation from the aragonite crystal form to the calcite crystal form.

[0100] Figure 5 A is a comparison graph of the fluorescence quantum yield of the blue phosphors prepared in Examples 1, 4, Comparative Example 1, and Comparative Example 2. The graph shows that the fluorescence quantum yield of the phosphor obtained by washing and drying with anhydrous ethanol is significantly higher than that obtained by washing and drying with ultrapure water. The graph also shows that the fluorescence quantum yield of the blue phosphor without the addition of PEG2000 and SDS is 74.65%, lower than that with the addition of dual template agents; and, under the condition that the mass ratio of PEG2000 to SDS is 1:1, the blue phosphor with the highest fluorescence quantum yield (94.28%) is prepared when the total content of both is 5%. Figure 5 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Examples 1, 5 and Comparative Example 3. It can be seen from the graph that the quantum yield reaches the highest when the mass ratio of template agent PEG2000 to SDS is 1:1, which is higher than the quantum yield of blue phosphors prepared by adding only PEG2000 or only SDS as template agents.

[0101] Figure 6 The fluorescence spectrum of the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1 is shown. As can be seen from the figure, the maximum excitation wavelength of the blue phosphor B-CDs@CaCO3 / PEG / SDS is 360 nm, and the emission peak is located at 437 nm. The spectrum retains the optical property of independent excitation of the B-CDs solution.

[0102] Figure 7 A, Figure 7 B. Figure 7C represents scanning electron microscope images of green phosphors prepared under different conditions with an addition amount of 7% (w / v) in Comparative Example 5, Example 2, and Comparative Example 4, respectively. Figure 7 As can be seen from Figure A, without the addition of template agents PEG2000 and SDS, the prepared phosphor exhibits obvious aggregation and irregular aggregate shapes; from Figure 7 As can be seen from B, the G-CDs@CaCO3 / PEG / SDS phosphor prepared according to Example 2 has a relatively regular sphere morphology and a rough surface; from Figure 7 As can be seen from Figure C, the phosphor obtained by washing with ultrapure water exhibits an irregular blocky structure.

[0103] Figure 8 Transmission electron microscopy image of the phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2. From... Figure 8 A and Figure 8 As can be seen from B, G-CDs@CaCO3 / PEG / SDS are composed of spherical nanosheets, which in turn are composed of smaller nanoparticles, and G-CDs are uniformly distributed on these nanoparticles.

[0104] Figure 9 Fourier transform infrared (FTIR) spectra of G-CDs prepared in Example 2, G-CDs@CaCO3 / PEG / SDS phosphor, G-CDs@CaCO3 phosphor prepared in Comparative Example 5, and up-waterwash phosphor prepared in Comparative Example 4 with a 7% (w / v) addition amount after washing with ultrapure water. The figures show that the absorption peaks of G-CDs are due to OH, C=C, and COO₂. - The stretching vibrations of CN and COC were observed. It was also observed that G-CDs@CaCO3 / PEG / SDS exhibited stretching vibrations at 3397 cm⁻¹. - The absorption peak at ¹ is attributed to the -OH stretching vibration of hydroxyl groups on the surface of G-CDs and the terminal hydroxyl groups of PEG2000; 1433 cm⁻¹ - ¹ and its acromion 1478 cm - ¹、877 cm - ¹ and 743cm - ¹ represents CO3 in CaCO3 2- The characteristic absorption peaks correspond, in turn, to in-plane bending, out-of-plane bending, and lattice vibrations, indicating that CaCO3 is the main crystal form of this composite material; 1085 cm⁻¹ - ¹ and 1130 cm -¹ is either a characteristic stretching vibration peak of the PEG2000 polyether bond COC or contributed by oxygen-containing functional groups on the surface of G-CDs. Furthermore, some characteristic peaks of G-CDs did not appear on the G-CDs@CaCO3 / PEG / SDS spectrum, indicating successful G-CDs encapsulation and confirming the successful preparation of the G-CDs@CaCO3 / PEG / SDS composite. The up-waterwash infrared spectrum of the material in Comparative Example 4, with 7% (w / v) added and washed with ultrapure water, shows that washing with ultrapure water increased the functional groups on the composite surface and shifted the position of the calcium carbonate characteristic peak, suggesting that the crystal structure of calcium carbonate was disrupted. The spectrum of G-CDs@CaCO3 in Comparative Example 5 shows that calcium carbonate at 1433 cm⁻¹... -1 The characteristic peak at 1478 cm did not appear. -1 The presence of shoulder peaks indicates that the addition of the template agent altered the crystal structure of calcium carbonate.

[0105] Figure 10 The X-ray diffraction spectra of the phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, the phosphor up-water wash prepared in Comparative Example 4 with an addition of 7% (w / v) and washed with ultrapure water, and the phosphor G-CDs@CaCO3 prepared in Comparative Example 5 are compared. As can be seen from the figures, the diffraction peak positions of the phosphors prepared under the three conditions correspond almost completely to the standard cards of the corresponding calcite-type CaCO3. This is because the unique surface states of green carbon dots tend to induce the formation of thermodynamically stable calcite crystals under the dual-template system of this invention, rather than metastable aragonite. However, the G-CDs@CaCO3 prepared in Comparative Example 5 has the strongest crystal intensity, while the composite material up-water wash obtained from ultrapure water washing has the weakest crystal intensity. The results above show that the addition of template agents PEG2000 and SDS reduces the crystallinity of CaCO3. This reduction in crystallinity is precisely the microscopic evidence that carbon dots have been successfully introduced into the lattice and effectively coated. Washing with ultrapure water will destroy the structure of calcium carbonate and thus reduce its calcite crystal strength.

[0106] Figure 11A is a comparison graph of the fluorescence quantum yield of the green phosphors prepared in Examples 2, 6, 4, and 5. The graph shows that the fluorescence quantum yield of the phosphor obtained by washing and drying with anhydrous ethanol is significantly higher than that obtained by washing and drying with ultrapure water. The graph also shows that the fluorescence quantum yield of the green phosphor without the addition of PEG2000 and SDS is 79.62%, lower than that with the addition of dual template agents; and, under the condition that the mass ratio of PEG2000 to SDS is 1:1, the green phosphor with the highest fluorescence quantum yield (97.29%) is prepared when the total content of both is 7%. Figure 11 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Examples 2, 7 and Comparative Example 6. It can be seen from the graph that the quantum yield reaches the highest when the mass ratio of template agent PEG2000 to SDS is 1:1, which is higher than the quantum yield of green phosphors prepared by adding only PEG2000 or only SDS as template agents.

[0107] Figure 12 The image shows the fluorescence spectrum of the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2. As can be seen from the image, the maximum excitation wavelength of the green phosphor G-CDs@CaCO3 / PEG / SDS is 503 nm, and the emission peak is located at 525 nm. The spectrum retains the optical property of independent excitation of the G-CDs solution.

[0108] Figure 13 A, Figure 13 B. Figure 13 C represents scanning electron microscope images of orange phosphors prepared under different conditions according to Comparative Example 8, Example 3, and Comparative Example 10. Figure 13 As can be seen from A, without the addition of template agents PEG2000 and SDS, the prepared phosphor exhibits obvious agglomeration, and the aggregates are composed of typical calcite flakes; from Figure 13 As can be seen from B, the O-CDs@CaCO3 / PEG / SDS phosphor prepared according to Example 3 has the morphology of regular spheres with a plate-like structure on the surface; from Figure 13 As can be seen in C, the phosphor obtained by washing with anhydrous ethanol exhibits an irregular spindle-shaped structure.

[0109] Figure 14 The image shows a transmission electron microscope (TEM) image of the phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3. As can be seen from the image, this is a circular sheet with a diameter of less than 200 nm, on which O-CDs are uniformly distributed. This indicates that O-CDs@CaCO3 / PEG / SDS is formed by the aggregation of circular nanosheets, and the O-CDs are successfully encapsulated within calcium carbonate.

[0110] Figure 15 Fourier transform infrared (FTIR) spectra of O-CDs prepared in Example 3, phosphor O-CDs@CaCO3 / PEG / SDS, phosphor O-CDs@CaCO3 prepared in Comparative Example 8, and phosphor anhydrous ethanol wash prepared in Comparative Example 10. The figures show that the absorption peak of O-CDs is due to the stretching vibrations of OH, C=O, N-aryl, and COC. It can also be seen that O-CDs@CaCO3 / PEG / SDS has a peak at 2919 cm⁻¹. - ¹and 2849 cm - The absorption peak at ¹ corresponds to the CH stretching vibration of the methylene (-CH2-) group in the PEG2000 molecule; 1392 cm⁻¹ - The peak at ¹ originates from the bending vibration of the methyl group (-CH3) in the SDS molecule, which is superimposed on the in-plane bending vibration of CO in CaCO3; 1240 cm⁻¹ - ¹、1211 cm - The double absorption peak at ¹ is contributed by the asymmetric stretching vibration of COC in the PEG molecular chain and the S=O stretching vibration in the SDS molecule; 1102 cm⁻¹ - The absorption peak at ¹ is a characteristic peak of the CO stretching vibration of PEG2000, and it superimposes with the COS stretching vibration of SDS; 964 cm⁻¹ - The peak at ¹ corresponds to the CO bending vibration of PEG and the characteristic vibration of the alkyl chain of SDS; 873 cm⁻¹ - ¹、853 cm - The absorption peak at ¹ is a characteristic peak of the out-of-plane bending vibration of CO in calcite-type CaCO3, at 713 cm⁻¹. - The peak at position ¹ is a characteristic peak of lattice vibration of calcite-type CaCO3, confirming that CaCO3 in the complex exists in the calcite crystal form; 624 cm⁻¹ - The peak at position ¹ corresponds to the superposition signal of the SO bending vibration and the Ca-O bond vibration of SDS. These characteristic peaks indicate that the orange phosphor O-CDs@CaCO3 / PEG / SDS was successfully prepared. The infrared spectrum of the material washed with anhydrous ethanol (Comparative Example 10) shows that its absorption peaks are significantly fewer than those of the phosphor O-CDs@CaCO3 / PEG / SDS washed with ultrapure water. This indicates that anhydrous ethanol, due to its amphiphilic nature, dissociates and strips the strongly adsorbed SDS molecules, disrupting the bonding between the template agent, the alcohol-loving carbon dots, and calcium carbonate, thus affecting the fluorescence properties of the composite material. The spectrum of O-CDs@CaCO3 (Comparative Example 8) shows that it almost lacks absorption peaks from the functional groups on the carbon dot surface, indicating that O-CDs can be coated with calcium carbonate.

[0111] Figure 16 The X-ray diffraction spectra of O-CDs@CaCO3 / PEG / SDS prepared in Example 3, the phosphor prepared by washing with anhydrous ethanol in Comparative Example 10, and the O-CDs@CaCO3 prepared in Comparative Example 8 are compared. The figures show that the diffraction peak positions of the phosphors prepared under the conditions of Example 3 and Comparative Example 8 correspond almost completely to the standard cards of the corresponding calcite-type CaCO3. The O-CDs@CaCO3 prepared in Comparative Example 8 has a stronger crystal intensity, indicating that the addition of the template agents PEG2000 and SDS reduces the crystallinity of CaCO3. The diffraction peaks of the phosphor prepared in Comparative Example 10 correspond to the standard card of aragonite-type calcium carbonate, indicating that anhydrous ethanol maintains the calcium carbonate in a metastable structure. This structure is not tightly packed, leaving pores or gaps, which easily leads to the loss of alcohol-loving carbon dots during washing with anhydrous ethanol. Therefore, considering the characteristics of orange-light carbon dots, in order to obtain a higher fluorescence quantum yield, this invention chooses to prepare orange-light phosphors by washing with ultrapure water, even though this leads to a crystal transformation to calcite. Although water washing induces a phase transition from metastable aragonite to stable calcite, due to the interfacial effect between O-CDs and ultrapure water, the O-CDs are successfully locked in the transformed lattice, achieving a balance between high quantum yield and structural stability.

[0112] Figure 17 A is a comparison graph of the fluorescence quantum yield of the orange phosphors prepared in Example 8, Comparative Example 7, and Comparative Example 8. The graph shows that the fluorescence quantum yield of the phosphors obtained by washing and drying with ultrapure water is generally higher than that obtained by washing and drying with anhydrous ethanol. The graph also shows that the fluorescence quantum yield of the orange phosphor is 35.88% without the addition of PEG2000 and SDS; and that, with a PEG2000 to SDS mass ratio of 1:1 and a total content of 5%, a higher fluorescence quantum yield of 85.33% was obtained. Figure 17 B is a comparison graph of the fluorescence quantum yield of the phosphors prepared in Examples 3, 9 and Comparative Example 9. It can be seen from the graph that when the total content of template agent PEG2000 and SDS is 5%, the quantum yield reaches the highest level of 91.04% when the mass ratio is 2:3, which is higher than the quantum yield of orange phosphors prepared by adding only PEG2000 or only SDS as template agents.

[0113] Figure 18The image shows the fluorescence spectrum of the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3. As can be seen from the image, the maximum excitation wavelength of the orange phosphor O-CDs@CaCO3 / PEG / SDS is 560 nm, and the emission peak is located at 587 nm. The spectrum retains the optical property of independent excitation of the O-CDs solution.

[0114] Figure 19 A, Figure 19 B. Figure 19 C shows the emission spectra of blue LEDs (B-LEDs), green LEDs (G-LEDs), and orange LEDs (O-LEDs) prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3. Their emission wavelengths are located at 455 nm, 518 nm, and 607 nm, respectively. The insets are photographs of the emission of blue, green, and orange LEDs at 3V, showing that the LEDs produce bright blue, green, and orange light. Figure 19 The CIE1931 coordinates shown in D are (0.16, 0.20), (0.23, 0.53), and (0.45, 0.33).

[0115] Figure 20 The optical properties of white LEDs (WLEDs) prepared using the blue phosphor B-CDs@CaCO3 / PEG / SDS prepared in Example 1, the green phosphor G-CDs@CaCO3 / PEG / SDS prepared in Example 2, and the orange phosphor O-CDs@CaCO3 / PEG / SDS prepared in Example 3 are described. Figure 20 It was found that by adjusting the mass ratio of B-CDs@CaCO3 / PEG / SDS, G-CDs@CaCO3 / PEG / SDS, and O-CDs@CaCO3 / PEG / SDS to 1:7:2, white LEDs (WLEDs) were successfully prepared. Figure 20 The fluorescence spectrum of the AWLED at 3V shows that the emission of the prepared WLED covers the entire visible light region (420~700 nm), and from... Figure 20 The illustration in A shows that the LED device emits bright white light when powered on. From Figure 20 As can be seen from B, the CIE coordinates of the prepared WLED are (0.31, 0.32), which are close to the CIE 1931 chromaticity coordinates of the standard WLED.

[0116] This invention provides a method for preparing high quantum yield phosphors of calcium carbonate-coated carbon dots with dual template regulation. The method is simple to operate, uses inexpensive raw materials, is environmentally friendly, and can achieve high fluorescence quantum yield of carbon dots in the solid state.

[0117] 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 within the protection scope of the present invention.

Claims

1. A method for preparing a high quantum yield phosphor of calcium carbonate-coated carbon dots regulated by dual templates, characterized in that, Includes the following steps: (1) Preparation of carbon dot solution: Add carbon dots to ethylene glycol and adjust to a certain absorbance to obtain carbon dot solution; (2) Add a certain amount of template agent and anhydrous calcium chloride to the carbon dot solution in step (1) to obtain mixed solution A; (3) Dissolve anhydrous sodium carbonate in ethylene glycol to obtain mixed solution B; (4) While stirring, slowly add the mixed solution B from step (3) to the mixed solution A from step (2). After the addition is complete, stir for a period of time to allow it to react fully. Then, age the reaction solution at room temperature to obtain the composite product. The composite product was centrifuged to collect the precipitate, which was then washed with a washing solvent and dried to obtain a high quantum yield phosphor.

2. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by dual templates according to claim 1, characterized in that, The carbon dots in step (1) are selected from any one of blue carbon dots, green carbon dots, and orange carbon dots.

3. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots controlled by dual templates according to claim 1, characterized in that, In step (1), the absorbance of the carbon dot solution is adjusted to 1.8 to 2.

5.

4. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by dual templates according to claim 1, characterized in that, In step (2), the template agent is any one or two of polyethylene glycol 400, polyethylene glycol 2000, polyethylene glycol 10000, polyacrylic acid, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, and sodium oleate.

5. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by dual templates according to claim 4, characterized in that, In step (2), the template agent is a mixture of polyethylene glycol 2000 and sodium dodecyl sulfate.

6. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots controlled by dual templates according to claim 1, characterized in that, The volume ratio of mixed solution A and mixed solution B in step (4) is (2-3):

1.

7. The method for preparing a high quantum yield phosphor with calcium carbonate-coated carbon dots regulated by dual templates according to claim 1, characterized in that, The centrifugation conditions in step (4) are 10,000 rpm for 5 min.

8. A fluorescent powder, characterized in that, It was prepared using the method for preparing high quantum yield phosphors with calcium carbonate-coated carbon dots controlled by dual templates as described in any one of claims 1 to 7.

9. The phosphor according to claim 8, characterized in that, The phosphor is a blue phosphor with an emission peak wavelength of 410-500nm in the excitation wavelength range of 305-400nm, or a green phosphor with an emission peak wavelength range of 520-550nm in the excitation wavelength range of 480-515nm, or an orange phosphor with an emission peak wavelength range of 570-600nm in the excitation wavelength range of 515-570nm.

10. The application of a phosphor prepared by the preparation method according to any one of claims 1 to 7, or a phosphor according to any one of claims 8 to 9, characterized in that, The phosphor is used to prepare LED devices, display devices, laser lighting, or luminescent materials.

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