A red light quantum dot coated fluorescent powder, a preparation method and application thereof

Abstract

The present application relates to the field of fluorescent powder preparation, especially to a red light fluorescent powder coated with quantum dots and a preparation method and application thereof.A red light fluorescent powder with high light-emitting thermal stability and high temperature resistance is excited by blue light, and the general formula of the combination ratio is K 1.9 (MEA) 0.1 TiF6: x Mn 4+ @GQDs y mg / mol ; wherein 0.01<= x <=0.12, 1<= y <=10.The preparation method is ion exchange method and hydrothermal synthesis method, the raw materials are mixed and stirred at room temperature, then KF*2H2O, HF, K 1.9 (MEA) 0.1 TiF6: x Mn 4+ and GQDs are mixed and fully reacted, and the obtained mixture is washed and dried to obtain the final product.The fluorotitanate red light fluorescent powder of the present application can be excited by the blue light emitted by InGaN chip, has excellent high temperature fluorescent performance and heat resistance, and has good market prospect.

Description

Technical Field

[0001] This invention relates to the field of phosphor preparation, and in particular to a red phosphor coated with quantum dots, its preparation method, and its application. Background Technology

[0002] White light-emitting diodes (WLEDs) possess advantages such as high luminous efficiency, long lifespan, low power consumption, and environmental friendliness, and are considered a new generation of solid-state light-emitting devices. Currently, the most mature and commercially available WLEDs utilize a blue LED chip and a yellow phosphor (YAG:Ce). 3+ This is achieved through a combination of different technologies, but the lack of red light in this type of white light results in a high color temperature and low color purity, making it difficult to apply to backlights for general lighting and display devices. Adding red phosphors that can be excited by blue light during the encapsulation process can compensate for the lack of red components in the WLED spectrum, thereby improving the color rendering performance of WLEDs.

[0003] Among many red phosphors, Mn 4+ Activated fluoride red phosphors have attracted considerable attention from researchers due to their excellent luminescence properties, such as a strong broad excitation band in the blue region and a strong narrow band emission in the red region. Among them, K₂TiF₆:Mn 4+ Phosphors are widely reported for their high quantum efficiency (IQE). However, organic-inorganic hybrid fluorotitanate red phosphors have received little attention. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the insufficient red light intensity, thermal quenching, and Mn content in existing phosphors. 4+ To address the insufficient research on doped organic-inorganic hybrid potassium fluorotitanate red phosphors, this paper provides a method for preparing a blue-light-excited, organic-inorganic hybrid red phosphor with excellent luminescence intensity and thermal stability.

[0005] This invention provides a method for preparing a red phosphor coated with quantum dots, comprising the following steps: S11: Fluorotitanic acid (H2TiF6) and ethanolamine are added to an aqueous solution containing potassium carbonate (K2CO3) to react and obtain ethanolamine hexafluorotitanate solid K. 1.9 (MEA) 0.1 TiF6; where MEA stands for monoethanolamine; S12: Potassium fluoride (KF), potassium hexafluoromanganate (K2MnF6), and the ethanolamine hexafluorotitanate solid K 1.9 (MEA) 0.1 TiF6 was added to an aqueous solution of hydrogen fluoride, and the reaction was carried out for 20-28 h to obtain a red phosphor. S13: Mix solution A and solution B and react at 110-130℃ for 2-4 h to obtain the red phosphor coated with quantum dots; solution A is obtained by adding potassium fluoride and the red phosphor to an aqueous solution of hydrogen fluoride; solution B is obtained by adding graphene quantum dots (GQDs) to an aqueous solution of hydrogen fluoride.

[0006] This invention synthesizes potassium fluorotitanate red phosphors containing and without ethanolamine, and further coats graphene quantum dots in addition to those containing ethanolamine. The luminescence properties of the three are then analyzed and compared.

[0007] Preferably, the concentration of hydrogen fluoride in the aqueous solution is 35-45 wt%.

[0008] Preferably, in step S11, the molar ratio of fluorotitanic acid, ethanolamine and potassium carbonate is (400-500):(20-25):(200-230).

[0009] Preferably, in step S12, potassium fluoride, potassium hexafluoromanganate, and the solid K... 1.9 (MEA) 0.1 The mass ratio of TiF6 was (1-3):(0.30-0.45):(5.5-6.6). The red phosphor was prepared using an ion exchange method.

[0010] Preferably, in step S12, solid K 1.9 (MEA) 0.1 The concentration of TiF6 in aqueous hydrogen fluoride solution is 0.02-0.03 g / mL.

[0011] Preferably, in step S12, the reaction method is to let it stand at room temperature (25±5℃) for 20-28 h, then filter it, wash it with ethanol 2-4 times, and dry it at 65-75℃ for 2-4 h.

[0012] Preferably, in step S13, the mass ratio of potassium fluoride, red phosphor and graphene quantum dots is (0.2-0.4):(4.2-5.2):(0.00028-0.00036); the reaction at 110-130℃ for 2-4 h in step S13 is a hydrothermal synthesis method.

[0013] Preferably, the graphene quantum dots (GQDs) are amino-based graphene quantum dots.

[0014] Preferably, the concentration of red phosphor in solution A is 0.3-0.4 g / mL.

[0015] Preferably, the concentration of graphene quantum dots in solution B is 0.06-0.07 mg / mL.

[0016] Preferably, in step S13, the reaction is followed by filtration, washing with ethanol 2-4 times, and drying at 65-75℃ for 2-4 hours.

[0017] The present invention also provides a red phosphor coated with quantum dots prepared by the above preparation method.

[0018] Preferably, the general formula of the red phosphor coated with quantum dots is: K 1.9 (MEA) 0.1 TiF6: x Mn 4+ @GQDs y Where x is Mn 4+ and K 1.9 (MEA) 0.1 The molar ratio of TiF6, where y is the relative amount of graphene quantum dots per mole of K. 1.9 (MEA) 0.1 The quality of TiF6.

[0019] Furthermore, the value of x is 0.01-0.12, and the value of y is 1-10 mg / mol.

[0020] Furthermore, x = 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 or 0.14, and y = 1, 2, 4, 6, 8 or 10.

[0021] Specifically, the general formula of the red phosphor coating quantum dots is K. 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol .

[0022] The present invention also provides a white light-emitting diode comprising the above-mentioned red phosphor coated with quantum dots.

[0023] Preferably, the excitation wavelength of the white light-emitting diode is 467 nm.

[0024] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: The method of this invention has the advantages of simple and easy-to-control experimental process, abundant and inexpensive raw materials, and ease of industrial production. A key feature of this invention is the use of an excitation wavelength of 467 nm, which matches the wavelength of commercial blue LED chips. This allows the excitation light to be excited by commercial blue LED chips and emit strong fluorescence at 590-650 nm, resulting in red phosphors with excellent luminescence intensity and thermal stability. Attached Figure Description

[0025] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0026] Figure 1 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol X-ray diffraction (XRD) pattern of K2TiF6 standard card.

[0027] Figure 2 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The emission spectrum (PL).

[0028] Figure 3 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The excitation spectrum (PLE) of the spectrum.

[0029] Figure 4 K prepared in Example 2 of the present invention 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The color coordinate diagram (CIE).

[0030] Figure 5 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9(MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The graph shows the changes in fluorescence intensity at high temperatures. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] In the following examples and comparative examples, the graphene quantum dots (GQDs) are all aminated graphene quantum dots, purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., model number XF092.

[0033] Example 1: [K] 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ Preparation of ] First, 73.74 g (450 mmol) of H₂TiF₆ and 1.37 g (22.5 mmol) of ethanolamine were weighed into a plastic beaker using an electronic balance and stirred. Then, a solution prepared from 29.54 g (213.75 mmol) of K₂CO₃ and 32 mL of H₂O was slowly added to the mixture. After thorough mixing, the mixture was dried at 70 °C for 4 h to obtain K. 1.9 (MEA) 0.1 TiF6.

[0034] Next, 2.5 g of KF•2H2O was weighed into a plastic beaker using an electronic balance. 15 mL (40 wt%) of HF was measured using a graduated cylinder and poured into the beaker, then stirred to dissolve the solid. 0.37 g (1.5 mmol) of K2MnF6 and 23.5 mmol of K were then weighed. 1.9 (MEA) 0.1 TiF6 was slowly added to the stirred solution. The solution was allowed to stand at room temperature for 24 hours. After standing, the solution was filtered, washed three times with anhydrous ethanol, dried under vacuum, and then placed in an oven at 70°C for 3 hours. After drying, the organic-inorganic hybrid Mn was obtained. 4+ Single-doped sample (K) 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ Red fluorescent powder.

[0035] Example 2: [K] 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol Preparation of ] First, weigh 0.5 g of KF•2H2O into a plastic beaker using an electronic balance. Then, measure 15 mL (40%) of HF using a graduated cylinder and pour it into the beaker, stirring to dissolve the solid. Next, weigh 20 mmol of KF•2H2O obtained in Example 1. 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ The powder is added to a beaker while stirring to form mixture one; In a hydrothermal reactor, 80 µL (4 mg / mL) of GQDs was dissolved in 5 mL of HF (40 wt%) and stirred to prepare mixture two. Mixture one was then added to mixture two and allowed to react completely. The hydrothermal reactor was then placed in an oven at 120 °C for 3 hours. After the reaction was complete, the mixture was filtered and washed three times with anhydrous ethanol. After drying, it was placed in an oven at 70 °C for 3 hours to obtain K. 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol Red phosphor.

[0036] Example 3: Preparation of red phosphor coated with quantum dots The method in this embodiment is the same as that in embodiment 2, except that the reaction is carried out at 110°C for 2 hours in an oven.

[0037] Example 4: Preparation of red phosphor coated with quantum dots The method in this embodiment is the same as that in embodiment 2, except that the reaction is carried out at 130°C in an oven for 4 hours.

[0038] Comparative Example 1: [K2TiF6:0.06Mn] 4+ Preparation of ] First, weigh 2.5 g of KF•2H2O into a plastic beaker using an electronic balance. Then, measure 15 mL of 40% HF using a graduated cylinder and pour it into the beaker, stirring to dissolve the solid. Next, weigh 0.37 g (1.5 mmol) of K2MnF6 and 23.5 mmol of K2TiF6, and slowly add them to the stirred solution. Let the solution stand at room temperature for 24 hours. After standing, filter the solution and wash it three times with anhydrous ethanol. After drying, place it in an oven at 70°C for 3 hours. After drying, obtain Mn... 4+ Single-doped sample (K2TiF6:0.06Mn) 4+ Red fluorescent powder.

[0039] Effect evaluation: Test methods: X-ray powder diffraction (XRD): Utilizing the diffraction effect of X-rays in crystals, phase and crystal structure analysis is performed by analyzing the position, number, and intensity of peaks after X-ray diffraction. The XRD instrument acquisition parameters used in this paper were: Cu-Kα radiation source, λ=0.154178 nm, scanning range 5-80°, scanning speed 5° / min. Photoluminescence excitation spectrum (PLE), emission spectrum (PL), and variable-temperature photoluminescence spectrum: all were obtained by fluorescence spectrometry, with a 450 W xenon lamp and a 150 W microsecond pulsed xenon lamp as excitation sources, equipped with the Tianjin Orient-KOJI high-temperature fluorescence instrument accessory (TAP-02). Based on the emission spectrum data obtained from the above PL test, the color coordinates of the sample were calculated using the CIE 1931 standard colorimetric system.

[0040] Testing equipment: X-ray powder diffractometer, model Rigaku D / Max-2500V, purchased from Rigaku Electric Co., Ltd., Japan. Fluorescence analyzer, model FLS980, purchased from Edinburgh Company, UK.

[0041] Figures 1 to 5 The test results are analyzed as follows: Figure 1 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The X-ray diffraction (XRD) patterns of the K2TiF6 standard card were also obtained. The diffraction peak positions of all samples were in high agreement with those of the standard card, and no impurity peaks were observed. This indicates that the doping of ethanolamine (MEA) and the surface coating of graphene quantum dots (GQDs) did not change the crystal structure of the matrix, and the prepared samples were pure phases.

[0042] Figure 2 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / molThe emission spectra (PL) of the samples were observed. Under 467 nm blue light excitation, all samples showed Mn emission at approximately 630 nm. 4+ The characteristic narrow-band emission peaks were observed. Among them, the luminescence intensity of Example 1 (MEA doped) was significantly higher than that of Comparative Example 1 (undoped MEA), while the luminescence intensity of Example 2 (further coated with GQDs) was the highest. This indicates that both MEA doping and GQDs coating can effectively enhance red light emission.

[0043] Figure 3 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The excitation spectra (PLE) of all samples consisted of a broad excitation band covering the blue light region of 300-550 nm, containing two main excitation peaks (approximately 350 nm and 467 nm). The strongest excitation peak was located at 467 nm, which perfectly matches the emission wavelength of commercial InGaN blue LED chips, indicating that the phosphor of this invention is very suitable for use in commercial white LEDs.

[0044] Figure 4 K prepared in Example 2 of the present invention 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / mol The color coordinates of the sample in Example 2 were calculated to be (0.69, 0.31), which are located in the deep red region of the CIE colorimetric diagram and are very close to the NTSC standard (color television standard) red coordinates (0.67, 0.33). This indicates that the phosphor can provide high-purity red light, effectively compensating for the lack of red component in commercial white LEDs.

[0045] Figure 5 The K2TiF6:0.06Mn prepared for Comparative Example 1 of this invention 4+ K prepared in Example 1 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ and K prepared in Example 2 1.9 (MEA) 0.1 TiF6:0.06Mn 4+ @GQDs 4 mg / molThe graph shows the change in fluorescence intensity at high temperatures. As the temperature increases from 30℃ to 200℃, the luminescence intensity of all samples first increases and then decreases. The sample in Example 2 (coated with GQDs) exhibits the best thermal stability, maintaining 264% of its luminescence intensity at 30℃ at 150℃, while the retention rates of Example 1 and Comparative Example 1 are only 234% and 217%, respectively. This demonstrates that the coating with GQDs significantly suppresses the thermal quenching effect of the phosphor.

[0046] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a red phosphor coated with quantum dots, characterized in that, Includes the following steps: S11: Fluorotitanic acid and ethanolamine are added to an aqueous solution containing potassium carbonate to react and obtain ethanolamine hexafluorotitanate solid; S12: Add potassium fluoride, potassium hexafluoromanganate and the solid ethanolamine hexafluorotitanate to an aqueous solution of hydrogen fluoride, and react for 20-28 h to obtain red phosphor. S13: Mix solution A and solution B and react at 110-130℃ for 2-4 h to obtain the red phosphor coated with quantum dots; solution A is obtained by adding potassium fluoride and the red phosphor to an aqueous solution of hydrogen fluoride; solution B is obtained by adding graphene quantum dots to an aqueous solution of hydrogen fluoride.

2. The preparation method according to claim 1, characterized in that: The concentration of hydrogen fluoride in the aqueous solution of hydrogen fluoride is 35-45 wt%.

3. The preparation method according to claim 1, characterized in that: In step S11, the molar ratio of fluorotitanic acid, ethanolamine and potassium carbonate is (400-500):(20-25):(200-230).

4. The preparation method according to claim 1, characterized in that: In step S12, the mass ratio of potassium fluoride, potassium hexafluoromanganate, and the solid ethanolamine hexafluorotitanate is (1-3):(0.30-0.45):(5.5-6.6).

5. The preparation method according to claim 1, characterized in that: In step S12, the concentration of ethanolamine hexafluorotitanate solid in the hydrogen fluoride aqueous solution is 0.02-0.03 g / mL.

6. The preparation method according to claim 1, characterized in that: In step S13, the mass ratio of potassium fluoride, red phosphor, and graphene quantum dots is (0.2-0.4):(4.2-5.2):(0.00028-0.00036).

7. A red phosphor coated with quantum dots prepared by the preparation method according to any one of claims 1-6.

8. The red phosphor coated with quantum dots according to claim 7, characterized in that: The general formula for the red phosphor coated with quantum dots is: K 1.9 (MEA) 0.1 TiF6: x Mn 4+ @GQDs y Where x is Mn 4+ and K 1.9 (MEA) 0.1 The molar ratio of TiF6, where y is the relative amount of graphene quantum dots per mole of K. 1.9 (MEA) 0.1 The quality of TiF6.

9. The red phosphor coated with quantum dots according to claim 8, characterized in that: The value of x is 0.01-0.12, and the value of y is 1-10 mg / mol.

10. A white light-emitting diode, characterized in that: The red phosphor that covers quantum dots as described in any one of claims 7-9.

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