Gallium Oxide Clusters with Tunable Green Fluorescence, Preparation Method and Use Thereof

Abstract

The present invention discloses a gallium oxide cluster with tunable green fluorescence, its preparation method and uses. The specific steps are as follows: After dissolving a carboxylic acid ligand and 4-methylpyrazole in a solvent, gallium acetylacetonate is weighed and added to a scintillation vial and then mixed with the above solution. A solvothermal reaction is carried out at a certain temperature, cooled to room temperature, and left to stand for slow evaporation. Crystals are precipitated after several days, and the product is obtained after centrifugation, washing and drying. A series of gallium oxide clusters prepared by the present invention have tunable green fluorescence properties, with the maximum excitation wavelength covering the range of 396 - 450 nm and having strong emission in the green light region around 495 - 539 nm. The absolute quantum yield of the product can reach 4.79% - 6.66%. At the same time, the main components of the product do not contain rare earth elements, and the preparation method is scientific, simple and effective, reducing the synthesis cost and environmental pollution. It can be used as a substitute for traditional rare earth fluorescent powders and applied in fields such as indoor and outdoor lighting.

Description

Technical Field

[0001] The present invention relates to a preparation method of a green phosphor with tunable function, in particular to a method for preparing a green phosphor with tunable function by using gallium oxide clusters. Background Art

[0002] White Light Emitting Diodes (WLEDs) have been successfully applied in the field of solid-state lighting due to their adjustable color temperature, low energy consumption, high performance, energy conservation and environmental protection. Currently, the main method to obtain white light is to excite one or more phosphors coated on the surface of a blue or ultraviolet / near-ultraviolet chip to achieve white light emission. Green phosphors are a key component of white LEDs, contributing the most to the overall luminous flux of WLED devices and indirectly affecting performance indicators such as the color rendering index, color temperature, and luminous efficiency of the devices. Most current green-emitting materials use expensive rare-earth ions such as Tb 3+ and Ce 3+ as activators and sensitizers of phosphors. The high production cost and the environmental damage caused during mining hinder the widespread use of rare-earth phosphors. Therefore, developing new and inexpensive non-rare-earth green-emitting phosphors using new technologies and designing green-emitting materials with tunable functions have important theoretical and practical significance for improving the performance and application of WLEDs. Summary of the Invention

[0003] One object of the present invention is to provide an inexpensive preparation method of gallium oxide clusters with green fluorescence properties, and tunable excitation wavelength, emission wavelength, and quantum yield.

[0004] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of gallium oxide clusters with tunable green fluorescence properties, comprising the following steps:

[0005] (1) Weigh a carboxylic acid ligand and 4-methylpyrazole, add them to a solvent to dissolve, and obtain a mixed solution; weigh gallium acetylacetonate and mix it with the above mixed solution, and dissolve it by ultrasonic treatment to obtain a miscible mixture;

[0006] (2) Place the miscible mixture in step (1) in an oven at a temperature of 100 - 120 °C for a solvothermal reaction for 72 - 120 h. After the reaction is completed, take out the miscible mixture and cool it. Let it stand at room temperature until the solvent volatilizes, and a blocky crystal product is precipitated;

[0007] (3) Dry the blocky crystal product under vacuum conditions to obtain gallium oxide clusters with tunable green fluorescence properties.

[0008] As a further improvement of the preparation method of gallium oxide clusters with tunable green fluorescence properties:

[0009] Preferably, the carboxylic acid ligand is one or a combination of two or more of benzoic acid, 3-fluorobenzoic acid, p-fluorobenzoic acid, 3-furoic acid, and 3,4,5,6-tetrafluorophthalic acid.

[0010] Preferably, in step (1), gallium acetylacetonate is weighed in a glove box under a nitrogen atmosphere and added to a scintillation vial, and then mixed with the mixed solution in the scintillation vial.

[0011] Preferably, in step (1), the molar ratio of gallium acetylacetonate, the carboxylic acid ligand, and 4-methylpyrazole is 1:(0.5 - 2):(3 - 6).

[0012] Preferably, the addition amount of gallium acetylacetonate in the solvent in step (1) is 33 mg / mL.

[0013] Preferably, the bulk crystal product in step (3) is washed with the solvent before drying.

[0014] Preferably, the solvent is N,N-dimethylformamide.

[0015] Preferably, the washed bulk crystal product in step (4) is dried under vacuum for more than 24 h.

[0016] The second object of the present invention is to provide a gallium oxide cluster having tunable green fluorescence properties prepared by the above preparation method.

[0017] The third object of the present invention is to provide a use of the above gallium oxide cluster having tunable green fluorescence properties in a white light emitting diode.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] 1) The intramolecular conjugated planar structure and the presence of electron-donating and electron-withdrawing groups at both ends of the molecule can tune the fluorescence properties of the substance. 4-Methylpyrazole and aromatic hydrocarbon carboxylic acid ligands not only have a strong π-π conjugation system, but also have electron-withdrawing groups such as carboxyl and fluorine, which can enhance the intermolecular charge transfer and form intermolecular hydrogen bonds, facilitating the regulation of the fluorescence properties of the substance. Secondly, the nitrogen and oxygen atoms in 4-methylpyrazole and carboxylic acid ligands have diverse coordination modes with metal ions, which can form rich novel metal cluster compounds and lead to the diversity of their luminescence behaviors, providing more possibilities for the regulation of their fluorescence properties. The present invention selects 4-methylpyrazole and carboxylic acid ligands to design and synthesize a green fluorescent metal cluster compound with tunable functions, which can provide new ideas for the preparation of green light-emitting materials in light-emitting devices. The present invention uses carboxylic acid ligands and pyrazolyl ligands (4-methylpyrazole) to delay the hydrolysis degree of gallium salts and simultaneously stabilize the gallium oxide cluster species in the solution.

[0020] 2) Carboxylic acid ligands and 4-methylpyrazole can not only delay the hydrolysis degree of gallium acetylacetonate, but also stabilize the gallium oxide cluster species in the solution, which is beneficial to crystallization. Moreover, they can control the size of the gallium oxide clusters formed in the solution. Different cluster sizes will cause red shifts or blue shifts in the fluorescence excitation wavelength and emission wavelength. By reasonably setting the ratio of carboxylic acid ligands, 4-methylpyrazole to gallium acetylacetonate, the three cooperate with each other to form stable gallium oxide clusters in the solution and grow gallium oxide cluster crystals.

[0021] 3) The preparation method in the present invention only needs one-step high-temperature heating to obtain a series of green phosphors with a wide wavelength range. The preparation method is scientific, simple and effective, reducing the synthesis cost and environmental pollution.

[0022] 4) Using EDS energy spectrum analysis for the target product prepared in the present invention, the results show that the main composition elements of the material are gallium, oxygen, carbon, nitrogen, and fluorine, without rare earth elements. The maximum excitation wavelength of the prepared gallium oxide clusters measured by the Edinburgh FLS-1000 steady-state fluorescence spectrometer covers the range of 396 - 450 nm, and has a strong emission in the green light region around 495 - 539 nm. The absolute quantum yield of the product can reach 4.79% - 6.66%. This shows that the prepared gallium oxide clusters have green fluorescence properties, and the excitation wavelength, emission wavelength and quantum yield can be tuned by adding different carboxylic acid ligands. Description of the Drawings

[0023] Figure 1 It is the result of EDS elemental analysis of the target products prepared by the preparation methods of Examples 1 - 5, corresponding to the gallium oxide clusters prepared by adding benzoic acid (A), 3-fluorobenzoic acid (B), p-fluorobenzoic acid (C), 3-furoic acid (D) and 3,4,5,6-tetrafluorophthalic acid (E) ligands respectively.

[0024] Figure 2 It is the emission spectrum of the target products prepared in Examples 1 - 5, corresponding to the gallium oxide clusters prepared by using benzoic acid, 3-fluorobenzoic acid, p-fluorobenzoic acid, 3-furoic acid, and 3,4,5,6-tetrafluorophthalic acid ligands respectively.

[0025] Figure 3 It is the excitation spectrum of the target products prepared in Examples 1 - 5, corresponding to the gallium oxide clusters prepared by using benzoic acid, 3-fluorobenzoic acid, p-fluorobenzoic acid, 3-furoic acid, and 3,4,5,6-tetrafluorophthalic acid ligands respectively. Detailed Embodiments

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0027] The preparation method of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] First, raw materials are purchased from the market: gallium acetylacetonate; 4-methylpyrazole; benzoic acid, 3-fluorobenzoic acid, p-fluorobenzoic acid, 3-furoic acid, 3,4,5,6-tetrafluorophthalic acid; N,N-dimethylformamide; scintillation vial.

[0029] Example 1

[0030] This example provides a preparation method of gallium oxide clusters with tunable green fluorescence properties, including the following steps:

[0031] S1. Weigh benzoic acid (40 mg, 0.328 mmol) and place it in a 10 mL centrifuge tube. Add 2 mL of anhydrous N,N-dimethylformamide solvent and 4-methylpyrazole (45 μL, 0.525 mmol) thereto, and ultrasonically dissolve and mix well. Weigh analytical pure gallium acetylacetonate (66 mg, 0.175 mmol) in a glove box protected by a nitrogen atmosphere and pour it into a 20 mL scintillation vial. Then add the above mixed solution to the vial and ultrasonically dissolve for 20 min.

[0032] S2. Preheat the oven to 100 °C, then quickly place the scintillation vial into the oven, set the oven temperature to 100 °C, react at this temperature for 120 h, turn off the oven, and take out the scintillation vial after cooling. Pale yellow block crystals will precipitate at the bottom, which are gallium oxide clusters.

[0033] S3. Wash the crystals three times with DMF solvent, dry them under vacuum conditions, and collect the product.

[0034] Example 2

[0035] This example provides a preparation method of gallium oxide clusters with tunable green fluorescence properties, including the following steps:

[0036] S1. Weigh 3-fluorobenzoic acid (24 mg, 0.175 mmol) and place it in a 10 mL centrifuge tube. Add 2 mL of anhydrous N,N-dimethylformamide solvent and 4-methylpyrazole (45 μL, 0.525 mmol) thereto, and ultrasonically dissolve and mix well. Weigh analytical pure gallium acetylacetonate (66 mg, 0.175 mmol) in a glove box protected by a nitrogen atmosphere and pour it into a 20 mL scintillation vial. Then add the above mixed solution to the vial and ultrasonically dissolve for 20 min.

[0037] S2. Preheat the oven to 120 °C, then quickly put the scintillation vial into the oven while it is hot. Set the oven temperature to 120 °C and react for 72 h at this temperature. Turn off the oven. After cooling, take out the scintillation vial, seal the scintillation vial with sealing film, and then pierce several small holes in the sealing film with a needle. Let it stand at room temperature to slowly volatilize the solvent. After 3 days, light yellow block crystals precipitate at the bottom of the vial, which is the gallium oxide cluster;

[0038] S3. Wash the crystals three times with DMF solvent, dry them under vacuum conditions, and collect the product.

[0039] Example 3

[0040] This example provides a preparation method of gallium oxide clusters with tunable green fluorescence properties, including the following steps:

[0041] S1. Weigh p-fluorobenzoic acid (i.e., 4-fluorobenzoic acid, 24 mg, 0.175 mmol) and place it in a 10 mL centrifuge tube. Add 2 mL of anhydrous N,N-dimethylformamide solvent and 4-methylpyrazole (45 μL, 0.525 mmol) to it, and dissolve and mix well by ultrasonic treatment. Weigh analytical pure gallium acetylacetonate (66 mg, 0.175 mmol) in a glove box protected by a nitrogen atmosphere and pour it into a 20 mL scintillation vial. Then add the above mixed solution into the vial and dissolve it by ultrasonic treatment for 20 min;

[0042] S2. Preheat the oven to 120 °C, then quickly put the scintillation vial into the oven while it is hot. Set the oven temperature to 120 °C and react for 72 h at this temperature. Turn off the oven. After cooling, take out the scintillation vial, seal the scintillation vial with sealing film, and then pierce several small holes in the sealing film with a needle. Let it stand at room temperature to slowly volatilize the solvent. After 2 days, light yellow block crystals precipitate at the bottom of the vial, which is the gallium oxide cluster;

[0043] S3. Wash the crystals three times with DMF solvent, dry them under vacuum conditions, and collect the product.

[0044] Example 4

[0045] This example provides a preparation method of gallium oxide clusters with tunable green fluorescence properties, including the following steps:

[0046] S1. Weigh 3-furoic acid (20 mg, 0.175 mmol) and place it in a 10 mL centrifuge tube. Add 2 mL of anhydrous N,N-dimethylformamide solvent and 4-methylpyrazole (90 μL, 1.020 mmol) to it, and dissolve and mix well by ultrasonic treatment. Weigh analytical pure gallium acetylacetonate (66 mg, 0.175 mmol) in a glove box protected by a nitrogen atmosphere and pour it into a 20 mL scintillation vial. Then add the above mixed solution into the vial and dissolve it by ultrasonic treatment for 20 min;

[0047] S2. Preheat the oven to 100 °C, then quickly put the scintillation vial into the oven while it is hot. Set the oven temperature to 100 °C and react for 120 h at this temperature. Turn off the oven. After cooling, take out the scintillation vial, seal the scintillation vial with a sealing film, and then pierce several small holes in the sealing film with a needle. Let it stand at room temperature to slowly volatilize the solvent. After 5 days, light yellow blocky crystals will precipitate at the bottom of the vial, which is the gallium oxide cluster.

[0048] S3. Wash the crystals three times with DMF solvent, dry them under vacuum conditions, and collect the product.

[0049] Example 5

[0050] This example provides a preparation method of gallium oxide clusters with tunable green fluorescence performance, including the following steps:

[0051] S1. Weigh 3,4,5,6-tetrafluorophthalic acid (i.e., tetrafluorophthalic acid, 21 mg, 0.088 mmol) and place it in a 10 mL centrifuge tube. Add 2 mL of anhydrous N,N-dimethylformamide solvent and 4-methylpyrazole (70 μL, 0.793 mmol) into it and dissolve and mix well by ultrasonic. Weigh analytical pure gallium acetylacetonate (66 mg, 0.175 mmol) in a glove box protected by a nitrogen atmosphere and pour it into a 20 mL scintillation vial. Then add the above mixed solution into the vial and dissolve it by ultrasonic for 20 min.

[0052] S2. Preheat the oven to 120 °C, then quickly put the scintillation vial into the oven while it is hot. Set the oven temperature to 120 °C and react for 72 h at this temperature. Turn off the oven. After cooling, take out the scintillation vial, and light yellow blocky crystals will precipitate at the bottom of the vial, which is the gallium oxide cluster.

[0053] S3. Wash the crystals three times with DMF solvent, dry them under vacuum conditions, and collect the product.

[0054] Analyze the gallium oxide clusters with tunable green fluorescence performance prepared using different carboxylic acid ligands in Examples 1-5:

[0055] 1) Characterize the products of Examples 1-5 using scanning electron microscopy combined with EDS energy spectrum analysis. The results Figure 1 show that the main constituent elements of the materials prepared in Examples 1 and 4 contain gallium, oxygen, carbon, and nitrogen, and do not contain rare earth elements; the main constituent elements of the materials prepared in Examples 2, 3, and 5 contain gallium, oxygen, carbon, nitrogen, and fluorine, and do not contain rare earth elements.

[0056] 2) Test the products of Examples 1-5 using an Edinburgh FLS-1000 steady-state fluorescence spectrometer. The results are as Figure 2 , and test their excitation wavelengths. The results are asFigure 3 ; It can be seen from Figure 2 and Figure 3 that:

[0057] The product of Example 1 exhibits green light emission with a maximum emission wavelength of 495 nm ( Figure 2 ), a maximum excitation wavelength of 405 nm ( Figure 3 ), an absolute quantum yield of 4.79%, and CIE color coordinates of (0.29, 0.42), indicating that the product emits green light.

[0058] The product of Example 2 exhibits green light emission with a maximum emission wavelength of 500 nm ( Figure 2 ), a maximum excitation wavelength of 406 nm ( Figure 3 ), an absolute quantum yield of 5.79%, and CIE color coordinates of (0.30, 0.43), indicating that the product emits green light.

[0059] The product of Example 3 exhibits green light emission with a maximum emission wavelength of 500 nm ( Figure 2 ), a maximum excitation wavelength of 406 nm ( Figure 3 ), an absolute quantum yield of 4.99%, and CIE color coordinates of (0.30, 0.43), indicating that the product emits green light.

[0060] The product of Example 4 exhibits green light emission with a maximum emission wavelength of 500 nm ( Figure 2 ), a maximum excitation wavelength of 396 nm ( Figure 3 ), an absolute quantum yield of 6.66%, and CIE color coordinates of (0.31, 0.44), indicating that the product emits green light.

[0061] The product of Example 5 exhibits green light emission with a maximum emission wavelength of 539 nm ( Figure 2 ), a maximum excitation wavelength of 450 nm ( Figure 3 ), an absolute quantum yield of 6.32%, and CIE color coordinates of (0.37, 0.47), indicating that the product emits green light.

[0062] The test results of the products prepared in the above Examples 1-5 confirm that the gallium oxide clusters prepared by the present invention have green fluorescence properties, and the excitation wavelength, emission wavelength, and quantum yield can be tuned by adding different carboxylic acid ligands.

[0063] The specific embodiments of the present invention have been described above. It should be understood that those skilled in the art can make various deformations and modifications to the gallium oxide clusters with tunable green fluorescence and its preparation method of the present invention. If the deformations and modifications to the present invention fall within the scope of the claims of the present invention, it does not affect the essence of the present invention.

Claims

1. A preparation method of gallium oxide clusters with tunable green fluorescence properties, characterized in that, It includes the following steps: (1) Weigh a carboxylic acid ligand and 4-methylpyrazole, add them to a solvent for dissolution to obtain a mixed solution; weigh gallium acetylacetonate and mix it with the above mixed solution, and dissolve it by ultrasonic treatment to obtain a miscible mixture; the carboxylic acid ligand is one or a combination of two or more of benzoic acid, 3-fluorobenzoic acid, p-fluorobenzoic acid, 3-furoic acid, and 3,4,5,6-tetrafluorophthalic acid; (2) Place the miscible mixture in step (1) in an oven at a temperature of 100-120 °C for solvothermal reaction for 72-120 h. After the reaction is completed, take out the miscible mixture and cool it. Let it stand at room temperature until the solvent volatilizes to precipitate a blocky crystal product; (3) Dry the blocky crystal product under vacuum conditions to obtain a gallium oxide cluster with tunable green fluorescence properties.

2. The preparation method of gallium oxide clusters with tunable green fluorescence performance according to claim 1, characterized in that In step (1), weigh gallium acetylacetonate in a glove box protected by a nitrogen atmosphere, add it to a scintillation vial, and then mix it with the mixed solution in the scintillation vial.

3. The preparation method of the gallium oxide cluster with tunable green fluorescence performance according to claim 1, characterized in that, In step (1), the molar ratio of gallium acetylacetonate, carboxylic acid ligand, and 4-methylpyrazole is 1:(0.5-2):(3-6).

4. The preparation method of gallium oxide clusters with tunable green fluorescence performance according to claim 1 or 3, characterized in that, The addition amount of gallium acetylacetonate in the solvent in step (1) is 33 mg / mL.

5. According to the preparation method of a gallium oxide cluster with tunable green fluorescence properties described in claim 1, before drying in step (3), the blocky crystal product is washed with the solvent.

6. According to the preparation method of a gallium oxide cluster with tunable green fluorescence properties described in claim 1 or 5, the solvent is N,N-dimethylformamide.

7. The preparation method of a gallium oxide cluster with tunable green fluorescence performance according to claim 1, characterized in that, In step (4), the washed blocky crystal product is dried under vacuum for more than 24 h.

8. A gallium oxide cluster with tunable green fluorescence properties prepared by the preparation method according to any one of claims 1-7.

9. Use of the gallium oxide cluster with tunable green fluorescence properties described in claim 8 in a white light emitting diode.

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