G-C3N4-doped mixed lanthanide series metal-organic framework white luminescent material and preparation method thereof

Abstract

The invention discloses a g-C3N4 doped mixed lanthanide series metal-organic framework white light-emitting material and a preparation method of the g-C3N4 doped mixed lanthanide series metal-organic framework white light-emitting material. The preparation method comprises the following steps: dissolving Tb < 3 + > metal salt and Eu < 3 + > metal salt in a proper amount of deionized water to prepare a solution, stirring and mixing the solution with a ligand, and transferring the mixed solution into a hydrothermal reaction kettle for hydrothermal reaction; centrifugally cleaning a product obtained after the reaction by using deionized water and absolute ethyl alcohol, and drying to obtain the Ln-MOFs luminescent material TbEu (cpioa) with yellow emission; dissolving the obtained clean and dry TbEu (cpioa) and g-C3N4 into deionized water, stirring and mixing, transferring into a hydrothermal reaction kettle, putting into a constant-temperature blast drying box, and carrying out hydrothermal reaction again, so as to finally obtain the white luminescent material. The prepared white light-emitting material and an ultraviolet LED chip are packaged into a light-emitting device, and the light-emitting device can emit high-color-rendering-index white light of which the luminous flux and the luminous intensity are more than ten times higher than those of Ln-MOFs.

Description

Technical Field

[0001] The present invention belongs to the field of new material technology inventions, and specifically relates to a method of doping gC 3 N 4 A method for preparing a mixed lanthanide metal MOFs luminescent material and a luminescent device thereof to improve the luminescence intensity. Background Art

[0002] Lanthanide metal-organic framework materials (Ln-MOFs) are a special type of luminescent MOF, which is prepared by doping rare earth elements into metal-organic frameworks (MOFs). They have the luminescent properties of both MOFs and rare earth materials. In order to achieve white light emission, Ln is usually introduced into the matrix material. 3+ As the luminescence center, by adjusting the Ln 3+ The ratio of nitrate can adjust the intensity of different colors of light, and finally the three colors of red, green and blue are synthesized into white light. Therefore, Ln 3+ Ion doping into metal-organic frameworks (Ln-MOFs) is considered to be one of the most promising materials for white light-emitting diode (WLED) applications.

[0003] At present, the preparation of LED devices is basically based on phosphors and light-emitting chips. There are three common ways to realize white light LEDs: (i) blue LED chips excite single-phase yellow or mixed green and red phosphors; (ii) near-ultraviolet LED chips excite red, green and blue phosphors; (iii) three monochromatic LEDs (red, green and blue) are combined. WLEDs composed of blue chips and yellow phosphors have advantages such as high luminous intensity, high efficiency, low cost and easy preparation, but inevitably have unstable and high color temperature due to the lack of red light due to the combination of yellow and blue light. In addition, there are disadvantages such as low color rendering index; the device prepared by combining near-ultraviolet chips and three-color red, green and blue phosphors has indeed greatly improved the color rendering index due to the addition of red light components, and also retains the advantages of high efficiency, but because its phosphor is in a three-phase state, it will have disadvantages such as unstable color temperature and high cost; the third method of obtaining white light by mixing red, green and blue three-color LED light has poor stability and is prone to color deviation due to changes in the fluorescence of a certain color LED. Therefore, in comparison, WLEDs made from single-phase white light-emitting Ln-MOFs phosphors have greater potential and have shown broad application prospects in the field of near-ultraviolet LEDs in recent years.

[0004] However, due to the ligand and Ln 3+ The existence of antenna effect between them makes the obtained white light emission weak. Therefore, Ln-MOF materials are compounded with other functional materials to achieve fluorescence synergy between different materials, while taking advantage of the diverse structure of MOF luminescence, the optical properties of the luminescent materials are significantly improved. Summary of the invention

[0005] The present invention proposes a method of doping gC 3 N 4 To improve the luminous intensity of mixed lanthanide metal MOFs luminescent materials and luminescent devices thereof, the yellow light emitting TbEu (cpioa) luminescent material is doped with gC having blue light emission. 3 N 4 , by changing gC 3 N 4 ratio with TbEu(cpioa) ultimately results in a stronger white light emission.

[0006] The technical solution steps adopted by the present invention are as follows:

[0007] 1. A single-phase gC 3 N 4 @TbEu(cpioa) white light emitting material:

[0008] C 3 N 4 @TbEu(cpioa) white light emitting material is firstly prepared by in-situ encapsulation method in the ligand H 3 Doping red and green luminescent centers Eu in cpioa 3+ and Tb 3+ Prepare TbEu(cpioa), then mix TbEu(cpioa) with gC 3 N 4 Synthesis of gC by hydrothermal method 3 N 4 @TbEu(cpioa) white light emitting material.

[0009] The hydrothermal synthesis process is completed in a polytetrafluoroethylene-lined hydrothermal reactor, and the final product is a white powder with good crystallinity and uniform particles.

[0010] Among them, H 3 The role of cpioa is to transfer energy to Tb through the antenna effect. 3+ Eu 3+ Green and red luminescent centers are obtained, and gC 3 N 4 The luminescent material can emit bright white light under the excitation of ultraviolet light with a wavelength of 365nm, and the luminescent spectrum covers the entire visible light range from blue light to red light. It is packaged into a light-emitting device with a commercially available LED chip to achieve bright white lighting at a voltage of 3.0 to 3.4V.

[0011] C 3 N 4The introduction of provides strong blue light, so there is no need to introduce La 3+ , so that more Tb can be introduced into the ligand 3+ Eu 3+ , which also enhances the emission of green and red light, making it possible to regulate white light.

[0012] 2. A method for preparing a mixed lanthanide MOFs white light emitting material, the steps of the method are as follows:

[0013] 1) 5-(4-carboxyl-phenoxy)-isophthalic acid (H 3 cpioa), terbium salt and europium salt are placed in a beaker and deionized water is added to dissolve;

[0014] 2) stirring the mixed solution at room temperature for 30 minutes and adding dilute nitric acid solution to adjust the pH of the solution to 5-6;

[0015] 3) The above solution was transferred to a stainless steel reactor lined with polytetrafluoroethylene and placed in a constant temperature forced air drying oven for hydrothermal reaction. The reaction temperature was controlled at 120° C. and the reaction time was controlled at 72 hours.

[0016] 4) The reacted powder was centrifugally washed with deionized water and anhydrous ethanol, and dried at 60° C. for 24 hours to obtain TbEu(cpioa) yellow light emitting material;

[0017] 5) TbEu(cpioa) and gC 3 N 4 Dissolve in deionized water in a beaker and stir for 30 minutes;

[0018] 6) The above solution was transferred to a stainless steel reactor lined with polytetrafluoroethylene and placed in a constant temperature air drying oven for hydrothermal reaction. The reaction temperature was controlled at 80° C. and the reaction time was controlled at 24 hours.

[0019] 7) The powder was washed by centrifugation with deionized water and anhydrous ethanol, and dried at 60°C for 24 hours to obtain gC 3 N 4 @TbEu(cpioa) white light emitting material;

[0020] The lining of the hydrothermal reactor is made of polytetrafluoroethylene or PPL material, and the outer shell is made of stainless steel. The pressure in the reactor is controlled by the amount of solution added, and the reaction is carried out under high temperature and high pressure.

[0021] The white powder has fine and uniform particles, good dispersibility and high crystallinity, and has a broad blue emission peak, a narrow green emission peak and a sharp red light emission spectrum within the range of 350 to 650 nm.

[0022] 3.gC3 N 4 @TbEu(cpioa) white light emitting material application in WLED

[0023] 1) Add appropriate amount of organic silica gel into a beaker;

[0024] 2) Weigh the gC 3 N 4 @TbEu(cpioa) white light emitting material, organic silica gel A and organic silica gel B glue are uniformly mixed in proportion (1.5:4:1);

[0025] 3) coating the uniform mixture on a 365nm UV LED chip;

[0026] 4) Place the packaged WLED in an oven and bake at 100° C. for 6 hours to cure.

[0027] The present invention has the following beneficial effects:

[0028] 1) The present invention obtains a doped gC by a simple hydrothermal synthesis method. 3 N 4 gC with stronger white light emission 3 N 4 @TbEu(cpioa) white light emitting material.

[0029] 2)gC 3 N 4 @TbEu (cpioa) white light emitting material encapsulated WLED emits bright white light at a voltage of 3.0V to 3.4V, with a color rendering index of 89.5, a color temperature of 4534K, and a luminous flux and luminous efficacy of 1.59lm and 2.25lm / W.

[0030] 3) The light-emitting device of the present invention and the undoped gC 3 N 4 Compared with LaTbEu(cpioa), the luminous flux and luminous efficiency are improved by more than ten times, proving its potential application in the field of luminescence. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a hydrothermal reactor: 1-fixing screws, 2-upper end cover, 3-reactor body, 4-sealing gasket, 5-lower end cover, 6-lining cover, 7-lining;

[0032] Figure 2 This is the X-ray diffraction pattern obtained in Example 1;

[0033] Figure 3 is the TEM spectrum of the product obtained in Example 1;

[0034] Figure 4 The product gC obtained in Example 1 3 N 4 @X-ray photoelectron spectrum of TbEu(cpioa);

[0035] Figure 5 is the thermogravimetric spectrum of the product obtained in Example 1;

[0036] Figure 6 is the emission spectrum of the product obtained in Example 1;

[0037] Figure 7 is the CIE chromaticity diagram of the product obtained in Example 1;

[0038] Figure 8 It is the energy transfer mode existing in the product obtained in Example 1;

[0039] Fig. 9 An LED device formed by packaging the product obtained in Example 1 with an LED chip;

[0040] Fig.10 is the photoluminescence spectrum of the LED device formed by packaging the product obtained in Example 1 with LaTbEu(cpioa);

[0041] Fig.11 This is a physical picture of an LED device formed by packaging the product obtained in Example 3;

[0042] Fig.12 This is the electroluminescence spectrum of the LED device formed by packaging the product obtained in Example 3. DETAILED DESCRIPTION

[0043] like Figure 1 The figure shows a stainless steel reactor for hydrothermal reaction of the present invention. The inner lining 7 of the reactor body 3 is made of polytetrafluoroethylene or PPL material. The upper end surface of the inner lining 7 is provided with an inner lining cover 6. The lower end cover 5 and the upper end cover 2 installed by fixing screws 1 are provided above the inner lining cover 6. The lower end cover 5 and the reactor body 3 are sealed by a sealing gasket 4. The present invention puts the prepared reaction solution into the hydrothermal reactor. Under high temperature and high pressure, the solute molecules react to finally generate TbEu(cpioa) and gC 3 N 4 @TbEu(cpioa) powder. 3 N 4 @TbEu(cpioa) white light emitting material emits bright white light under the excitation of 365nm ultraviolet light. It is packaged into a light-emitting device with a commercially available LED chip to achieve bright white lighting at a voltage of 3.0 to 3.4V.

[0044] Embodiment 1:

[0045] C 3 N 4 Doped with TbEu(cpioa)

[0046] 8.6602 g of lanthanum nitrate hexahydrate, 9.0586 g of terbium nitrate hexahydrate and 8.9212 g of europium nitrate hexahydrate were respectively dissolved in 100 mL of deionized water and stirred for a period of time to obtain lanthanum nitrate, terbium nitrate and europium nitrate solutions with a molar concentration of 0.2 mol / L.

[0047] Reactor 1 is respectively measured with 3.6mL, 0.372mL and 0.028mL of lanthanum nitrate, terbium nitrate and europium nitrate solutions in a molar ratio of 0.9:0.093:0.007, reactor 2 is respectively measured with 3.96mL, 0.04mL of terbium nitrate and europium nitrate solutions in a molar ratio of 0.99075:0.00925, weigh 0.8mmol of 5-(4-carboxyl-phenoxy)-isophthalic acid 0.26085g, dissolve it in deionized water and add the mixed solution into two reactors 1 and 2, stir at room temperature for 30 minutes, during which dilute nitric acid solution is dripped into the solution to adjust the pH to 5-6. After stirring, the solution is transferred to a 100mL polytetrafluoroethylene liner with a filling degree of about 50%. The three reactors are placed in a constant temperature forced air drying oven for hydrothermal reaction, the reaction temperature is 120°C, and the reaction time is 72 hours. After the reaction was completed, the powders obtained from the four reactors were washed three times by centrifugation with deionized water and anhydrous ethanol respectively, and then placed in a constant temperature drying oven at 60° C. for 24 hours.

[0048] Weigh the TbEu(cpioa) obtained in reaction container 2, and weigh 50 mg of TbEu(cpioa) into reaction container 3. Add 0.075 mg of gC 3 N 4 Put it into the reaction container and mix it with TbEu(cpioa), add deionized water to dissolve it, and stir it at room temperature. After stirring, transfer the solution to a 100mL polytetrafluoroethylene liner. Put the reactor into a constant temperature blast drying oven for hydrothermal reaction, the reaction temperature is 80℃, and the reaction time is 24 hours. After the reaction is completed, the powder obtained from the reactor is centrifuged and washed 3 times with deionized water and anhydrous ethanol, and then placed in a constant temperature drying oven at 60℃ for 24 hours. Finally, white gC with fine and uniform particle size is obtained. 3 N 4 @TbEu(cpioa) powder.

[0049] Figure 2 For LaTbEu(cpioa), TbEu(cpioa) and gC 3 N 4@Ln(cpioa) XRD spectrum, the synthesized product in this spectrum is completely consistent with the standard spectrum. 3 N 4 After the formation of gC 3 N 4 @Ln(cpioa) Compared with the standard spectrum, it can be seen that the diffraction peak has a slight shift, but the overall framework remains unchanged, confirming that gC 3 N 4 The entry of La(cpioa) does not change its crystal structure.

[0050] Figure 3 The products LaTbEu(cpioa), TbEu(cpioa) and gC obtained in Example 1 are 3 N 4 @Ln(cpioa) transmission electron microscope photo. From this figure, we can get gC 3 N 4 @Ln(cpioa)There is not much difference in appearance, both are fragmented.

[0051] Figure 4 It is gC 3 N 4 @Ln(cpioa) powder X-ray photoelectron spectroscopy. From the XPS results, it can be concluded that gC 3 N 4 It binds to Ln(cpioa) through weak interactions.

[0052] Figure 5 The thermogravimetric curves of the three products obtained show that LaTbEu(cpioa), TbEu(cpioa) and gC 3 N 4 @Ln(cpioa) framework can maintain good thermal stability before 300℃, among which gC 3 N 4 @TbEu(cpioa) loses weight at 300℃, the reason may be gC 3 N 4 of falling off.

[0053] Figure 6 for LaTbEu(cpioa) and gC 3 N 4 @Ln(cpioa) fluorescence emission spectrum at room temperature, it can be seen that gC 3 N 4 @TbEu(cpioa)Higher emission intensity.

[0054] Figure 7are the CIE chromaticity coordinates corresponding to the emission spectrum, which are LaTbEu(cpioa):(0.36,0.36), gC 3 N 4 @TbEu(cpioa): (0.34, 0.37).

[0055] Figure 8 gC 3 N 4 @TbEu(cpioa) energy transfer simulation diagram. There may be two forms of energy transfer in the system: one is the energy transfer from organic ligand to metal ion (LMCT); the other is the energy transfer from metal ion Tb 3+ To Eu 3+ Energy transfer of ions (MMCT).

[0056] Because gC 3 N 4 With metal ions and H 3 The mismatch of cpioa energy levels is not conducive to energy transfer, so gC 3 N 4 It can always show strong blue light emission. In addition, in terms of white light modulation, when adding gC 3 N 4 No need to add La 3 + , more Tb can be added to the matrix 3+ and Eu 3+ , thus obtaining a stronger emission.

[0057] Fig. 9 for LaTbEu(cpioa) and gC 3 N 4 @Ln(cpioa)LED chip packaged light-emitting device, and the light-emitting picture at 3.2V voltage.

[0058] Embodiment 2:

[0059] Reactors 1, 2, and 3 were respectively weighed with 2.9715 mL and 0.03 mL of terbium nitrate and europium nitrate solutions in a molar ratio of 0.99075:0.00925, and 0.1956 g of 5-(4-carboxyl-phenoxy)-isophthalic acid was weighed and dissolved in deionized water, and the mixed solution was added to the three reactors 1, 2, and 3, and stirred at room temperature for 30 minutes. During this process, dilute nitric acid solution was dripped into reactor 1 to adjust the solution pH to 5-6, an equal volume of deionized water was dripped into reactor 2, and sodium hydroxide solution was dripped into reactor 3 to adjust the solution pH to 7-8. After stirring, the solution was transferred to a 100 mL polytetrafluoroethylene liner with a filling degree of about 50%. The three reactors were placed in a constant temperature blast drying oven for hydrothermal reaction, the reaction temperature was 120°C, and the reaction time was 72 hours. After the reaction was completed, the powders obtained from the three reactors were washed three times by centrifugation with deionized water and anhydrous ethanol respectively, and then placed in a constant temperature drying oven at 60° C. for 24 hours.

[0060] The TbEu(cpioa) obtained in reaction vessels 1, 2 and 3 were weighed, and the yields of reaction vessels 1, 2 and 3 were calculated to be 77.4%, 54.2% and 51.2%, respectively.

[0061] The experimental results show that a higher yield of TbEu(cpioa) can be obtained by adding dilute nitric acid under acidic conditions.

[0062] Embodiment 3:

[0063] 0.4 g of organic silica gel A and 0.1 g of organic silica gel B were added to reactors 1, 2, and 3 respectively, and mixed evenly. Then, 0.1 g, 0.15 g, and 0.2 g of gC were added to reactors 1, 2, and 3 respectively. 3 N 4 @TbEu(cpioa) was stirred and mixed evenly, and the uniform mixture was coated on a 365nm UV LED chip. The packaged LED was placed in an oven and baked at 100°C for 6 hours to obtain the final LED device.

[0064] like Fig.11 and Fig.12 As shown, the physical picture and electroluminescence spectrum prove that organic silica gel A: organic silica gel B glue: gC 3 N 4 @TbEu(cpioa)=4:1:1.5 can obtain the best luminescence.

Claims

1. A doped gC 3 N 4 Hybrid lanthanide metal-organic framework white luminescent materials, It is characterized in that Under ultraviolet light, yellow light emission of TbEu(cpioa) and blue light emission of gC 3 N 4 Doping to obtain gC with white light emission 3 N 4 @TbEu(cpioa) luminescent material.

2. A doped gC according to claim 1 3 N 4 Hybrid lanthanide metal-organic framework white luminescent materials, It is characterized in that By changing gC 3 N 4 @TbEu(cpioa)Tb 3+ and Eu 3+ The molar ratio of metal ions and gC 3 N 4 The mass ratio with TbEu(cpioa) regulates the luminescent color of the luminescent material; The white light emitting material contains Tb 3+ ,Eu 3+ The optimal molar ratio is 0.99075:0.00925, gC 3 N 4 The optimal mass ratio with TbEu(cpioa) is 100:0.

15.

3. A light-emitting device prepared using the white light-emitting material according to claim 1, Features: The light emitting device is prepared by the following method: 1) Add appropriate amount of organic silica gel into a beaker; 2) gC 3 N 4 @TbEu(cpioa) white light emitting material, organic silica gel A and organic silica gel B are uniformly mixed in a ratio of 1.5:4:1; 3) coating the uniform mixture on a 365nm ultraviolet LED chip for packaging; 4) Place the packaged WLED in an oven and bake at 100° C. for 6 hours to cure.

4. The light emitting device according to claim 3, Features: The light emitting device emits white light at a voltage of 3.0-3.4V, with a color rendering index of 89.5, a color temperature of 4534K, and a luminous flux and a luminous efficiency of 1.59lm and 2.25lm / W.

5. The method for preparing the white luminescent material according to claim 1, It is characterized in that The following steps are involved: Step 1) Tb 3+ and Eu 3+ The nitrate solutions were dissolved in deionized water respectively, stirred to prepare ion solutions; Step 2) Convert the Tb configured in step 1) to 3+ Solution, Eu 3+ Solution and organic ligand H 3 CPIOA was dissolved in deionized water, stirred at room temperature, and during the stirring process, dilute nitric acid was added dropwise to adjust the pH of the solution to acidic; Step 3) The solution of step 2) is transferred to a stainless steel reactor lined with polytetrafluoroethylene, and placed in a constant temperature forced air drying oven for hydrothermal reaction to obtain TbEu(cpioa); Step 4) washing the powder after the hydrothermal reaction in step 3) with deionized water and anhydrous ethanol, and drying at 60° C. for 24 hours; Step 5) TbEu(cpioa) obtained in step 4) and gC 3 N 4 Dissolve in deionized water and stir at room temperature for 30 minutes; Step 6) The solution of step 5) is transferred to a hot reaction kettle and placed in a constant temperature forced air drying oven for hydrothermal reaction; Step 7) The powder after the hydrothermal reaction in step 6) is washed with deionized water and anhydrous ethanol, and dried at 60° C. for 24 hours.

6. The preparation method according to claim 5, Features: In the step 1), the soluble terbium salt and europium salt are terbium nitrate and europium nitrate, or terbium chloride and europium chloride, respectively.

7. The preparation method according to claim 5, Features: In the step 2): Tb 3+ and Eu 3+ The molar ratio is 0.99075:0.00925; The organic ligand is 5-(4-carboxy-phenoxy)-isophthalic acid.

8. The preparation method according to claim 5, Features: In the step 2), The stirring time is 30 minutes; The concentration of dilute nitric acid is 0.1 M / L, and the pH of the solution is adjusted to 5-6 using dilute nitric acid.

9. The preparation method according to claim 5, Features: In the step 3), the reaction temperature of the hydrothermal reaction is controlled at 120° C. and the reaction time is controlled at 72 h; In the step 6), the reaction temperature of the hydrothermal reaction is controlled at 80° C., and the reaction time is controlled at 24 h.

10. The preparation method according to claim 5, Features: In the step 3), the inner lining of the thermal reaction kettle is made of polytetrafluoroethylene or PPL material, the outer shell is made of stainless steel material, and the filling degree of the solution in the thermal reaction kettle is 45% to 50%.

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