X-ray excited purple rare earth afterglow material and preparation method thereof

Abstract

The invention belongs to the field of afterglow materials and display. The invention discloses an X-ray excited purple rare earth afterglow material. The molecular formula of the X-ray excited purple rare earth afterglow material is CaFCl: Eu / Ce / Na. The preparation method sequentially comprises the following steps: uniformly mixing and grinding calcium fluoride, calcium chloride, europium chloride, cerium chloride and sodium chloride in proportion, carrying out high-temperature reaction in a tubular furnace, and carrying out heat preservation in a drying oven to obtain a product. The product has the characteristics that under the excitation of X rays, the product has very strong purple afterglow performance, the afterglow duration is more than 60 hours, and the product has a very good application prospect in the field of full-color afterglow display.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of afterglow materials and display, and relates to a rare earth ion doped fluorochloride material and its display application for afterglow full spectrum regulation. BACKGROUND

[0002] Long afterglow luminescence is an important optical phenomenon, which refers to the persistent emission of photons by a material after excitation ceases. This delayed photon emission has good application prospects in many fields, including optical data storage, night vision display, background-free medical diagnosis, and high-resolution radiography. Although this phenomenon was discovered in the early 17th century, efficient inorganic long afterglow luminescent materials are still mainly limited to blue light emitting systems (such as CaAl2O4:Eu / Nd) and green light emitting systems (such as SrAl2O4:Eu / Dy and Sr2MgSi2O 7: Eu / Dy). Longer wavelength emissions (such as yellow and red light) are usually achieved in sulfide-based materials, which have poor stability and low brightness. Efficient purple long afterglow luminescence has not been proven, especially using environmentally stable and scalable substrates.

[0003] There are also some related research and applications of X-ray excited rare earth afterglow materials in the prior art,

[0004] (1) For example, the invention patent application with the application number 202011538445.7 and the name of X-ray excited near-infrared two-region luminescence long afterglow nanoprobes, preparation method and application in vivo imaging analysis, utilizes the rich energy level structure of rare earth ions, realizes long afterglow luminescence in the near-infrared two-region by doping different rare earth ions under X-ray excitation, and proves the application prospect of these nanoprobes in deep tissue imaging. However, the afterglow nanoprobes of this application use a multiple epitaxial growth method, which is complex and not suitable for batch production. Moreover, the emission spectrum of this system is in the near-infrared two-region, not in the purple region.

[0005] (2) For another example, the invention patent application with the application number 202311466202.0 and the name of X-ray excited ultraviolet luminescence long afterglow material and its application in the field of high-level X-ray imaging encryption, the afterglow luminescence produced by this system is in the ultraviolet region which is invisible to the human eye, and the flexible memory film prepared can realize three-dimensional information encryption of curved objects. However, the emission spectrum of this system is in the ultraviolet region which is invisible to the human eye, not in the purple region.

[0006] (3) For example, the authorized invention patent with application number 202410362486.7, entitled "A Rare Earth Element Doped Phosphate Long Afterglow Material Excited Only by X-rays and Its Preparation Method and Application", describes a material that can only be excited by X-rays and produces bright green, purple, reddish-brown, and orange-red light visible to the naked eye. It cannot be excited by white light or ultraviolet light, so it will not be affected by natural light in daily life. Furthermore, after being irradiated by X-rays for a period of time, it can still be re-excited by hot water to emit bright green light, which can be used for daily personal and household X-ray dose detection. Although the system involves purple, the afterglow performance in this band needs to be improved.

[0007] (4) For example, the invention patent application with application number 202410696431.X, entitled "An X-ray Excited Borate Long Afterglow Luminescent Material and Its Preparation Method", can be excited by X-rays to produce long afterglow luminescence in the range of 300nm-400nm. The prepared borate long afterglow luminescent material can be mixed with organic polymer materials such as epoxy resin and curing agent to form a thin film, which can be used as a luminescent film or a blue afterglow luminescent device. However, it uses a borate system, and the rare earth ion used for purple luminescence is trivalent Pr. 3+ The afterglow performance needs to be improved. Summary of the Invention

[0008] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide an X-ray excited purple rare earth afterglow material that can produce bright purple afterglow emission after X-ray irradiation. The afterglow brightness is high and the duration is long, greater than 60 hours. It can be used to excite halide perovskite quantum dots to achieve full-spectrum modulation and display applications in the visible light region.

[0009] This invention is achieved using the following technical solution: an X-ray excited purple rare earth afterglow material with the molecular formula CaFCl:Eu / Ce / Na, whose afterglow luminescence integral intensity is superior to commercial CaAl2O4:Eu / Nd and SrAl2O4:Eu / Dy, and whose afterglow duration is greater than 60 hours.

[0010] A method for preparing X-ray excited violet rare-earth afterglow material includes the following steps:

[0011] Step 1: Mix and grind 10 mmol of calcium fluoride, 9.12-9.93 mmol of calcium chloride, 0.01-0.04 mmol of cerium chloride, 0.05-0.8 mmol of europium chloride, and 0.01-0.04 mmol of sodium chloride according to the molar percentage for 30-60 minutes.

[0012] Step 2: The mixture is reacted in a tube furnace for 1-3 hours at a temperature of 700-900℃, and a mixture of nitrogen and hydrogen is continuously introduced, with the hydrogen ratio being 5%.

[0013] Step three: After the reaction, the room is naturally cooled to room temperature, and during the cooling process, the nitrogen and hydrogen mixed gas is continuously introduced, and the proportion of hydrogen is 5%;

[0014] Step four: The product is kept in an oven at 80-130℃ for 1-3 hours, and after cooling to room temperature, CaFCl:Eu / Ce / Na afterglow material is obtained.

[0015] Compared with the prior art, the significant advantages of the present application are:

[0016] 1. A new structure system is constructed by doping two trace heterovalent ions, the molecular formula is CaFCl:Eu / Ce / Na, CaFCl is the matrix, divalent rare earth Eu 2+ ion is the luminescent center, and doping trace Ce 3+ ion can improve the energy transfer efficiency of trapped electrons to Eu 2+ ion, and Na + can improve the trap concentration and maintain the charge balance of the system by co-substituting Ca 3+ with Ce 2+ .

[0017] 2. The rare earth afterglow performance is significantly improved, and under X-ray excitation, the afterglow performance is about 80 times higher than that of CaFCl:Eu system, which is 3.5 times that of the most optimal commercial SrAl2O4:Eu / Dy system. The significant improvement in performance is mainly due to the synergistic effect of the increase in trap concentration and the improvement in energy transfer efficiency, which greatly improves the electron filling efficiency of the excited state energy level of Eu 2+ ion.

[0018] 3. The preparation method of the afterglow material is simple, which is the traditional high-temperature solid-phase sintering method, suitable for mass production, and low cost.

[0019] 4. The flexible transparent film prepared by using the afterglow material can be used to excite halide perovskite quantum dot systems of different components, so as to realize full-spectrum regulation and display application in visible light region. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 : X-ray diffraction pattern of CaFCl:Eu / Ce / Na in Example 1;

[0021] Figure 2 : Afterglow spectrum of CaFCl:Eu / Ce / Na in Example 1 after X-ray excitation is stopped;

[0022] Figure 3 : Afterglow spectrum of CaFCl:Eu / Ce / Na in Example 1 after X-ray excitation is stopped for 60 hours;

[0023] Figure 4 : The relationship curve of the intensity of the afterglow of CaFCl:Eu / Ce / Na in Example 1 after the X-ray excitation stopped and the concentration of Ce 3+ ion; 3+ The concentration of Ce ion was taken as a reference;

[0024] Figure 5 : The relationship curve of the intensity of the afterglow of CaFCl:Eu / Ce / Na in Example 1 after the X-ray excitation stopped and the concentration of Eu 2+ ion;

[0025] Figure 6 : Comparison of the afterglow spectrum of CaFCl:Eu / Ce / Na in Example 1 and the commercial CaAl2O4:Eu / Nd, SrAl2O4:Eu / Dy under the same test conditions;

[0026] Figure 7 : Comparison of the afterglow integral intensity of CaFCl:Eu / Ce / Na in Example 1 and the commercial CaAl2O4:Eu / Nd, SrAl2O4:Eu / Dy under the same test conditions;

[0027] Figure 8 : Comparison of the afterglow decay curve of CaFCl:Eu / Ce / Na in Example 1 and CaFCl:Eu in Comparative Example 1 under the same test conditions;

[0028] Figure 9 : Comparison of the afterglow integral intensity of CaFCl:Eu / Ce / Na in Example 1 and CaFCl:Eu in Comparative Example 1 under the same test conditions;

[0029] Figure 10 : The visible region spectrum regulation diagram based on CaFCl:Eu / Ce / Na in Example 1; the curves from left to right are CaFCl:Eu / Ce / Na, CsPbCl2Br1, CsPbCl1Br2, CsPbCl 0.5 Br 2.5 , CsPbBr1I2, CsPbBr 1.3 I 1.7 , CsPbBr2I1 and CsPbI3. DETAILED DESCRIPTION

[0030] The application will be further described below. Figures 1-10 with reference to the accompanying drawings.

[0031] Example 1

[0032] An X-ray excitation purple rare earth afterglow material, having a molecular formula of CaFCl:Eu / Ce / Na.

[0033] The preparation method of CaFCl:Eu / Ce / Na includes the following steps: (1) 10 mmol of calcium fluoride, 9.444 mmol of calcium chloride, 0.028 mmol of cerium chloride, 0.5 mmol of europium chloride, and 0.028 mmol of sodium chloride are mixed and ground evenly in proportion for 60 minutes; (2) The mixture is reacted in a tube furnace for 2 hours at a temperature of 800℃, and a mixture of nitrogen and hydrogen is continuously introduced, with a hydrogen ratio of 5%; (3) After the reaction is completed, the mixture is naturally cooled to room temperature. During the cooling process, a mixture of nitrogen and hydrogen is continuously introduced, with a hydrogen ratio of 5%; (4) The product is kept at 110℃ in an oven for 2 hours and cooled to room temperature to obtain CaFCl:Eu / Ce / Na afterglow material.

[0034] The CaFCl:Eu / Ce / Na afterglow material prepared by the above method was analyzed by powder X-ray diffraction, which showed that the product was a pure tetragonal phase. Figure 1 After 30 seconds of X-ray irradiation, the X-ray source was turned off, and the product exhibited divalent Eu. 2+ Characteristic transition lines, including 5d-4f transitions ( Figure 2 ); 60 hours later, the product irradiated by X-rays still had a strong emission spectrum, indicating that the afterglow time of the product was greater than 60 hours. Figure 3 ).

[0035] To prove Gd 3+ Ions can enhance afterglow luminescence performance by improving energy transfer efficiency. We compared different Ce... 3+ Afterglow properties of samples with high ion concentration. For example... Figure 4 As shown, with Ce 3+ As the ion concentration gradually increased from 0.05% (molar percentage) to 0.2%, the afterglow luminescence intensity was significantly improved, indicating that Ce doping... 3+ Ions can improve afterglow performance. Because Ce... 3+ The ion is trivalent, and the matrix ion Ba is substituted. 2+ Since Na has a +2 valence, in order to maintain the charge balance of the system, we introduce Na with a +1 valence. + Ions, via Ce 3+ Ions and Na + Simultaneously replaces two Ba atoms in the matrix lattice. 2+ Ions are used to maintain the electroneutrality of the system. In addition, Na... + Ion doping can effectively reduce the formation energy of Frankel defects. Under the same irradiation conditions, Na + Ions increase the trap concentration. Through the synergistic effect of increased trap concentration and improved energy transfer efficiency, the afterglow luminescence performance is significantly enhanced.

[0036] To further optimize the afterglow luminescence performance, we investigated the optimal Eu... 2+ Ion doping concentration. For example... Figure 5 As shown, with Eu 2+ As the ion doping concentration gradually increased from 0.25% (molar percentage) to 2.5%, the afterglow luminescence intensity was significantly improved, Eu 2+ When the ion doping concentration is too high, the afterglow luminescence intensity begins to weaken, indicating that the optimal Eu concentration is not yet reached. 2+ The ion doping concentration is 2.5%.

[0037] To compare the afterglow performance of this system with commercial systems CaAl2O4:Eu / Nd and SrAl2O4:Eu / Dy, we tested the afterglow spectra of CaFCl:Eu / Ce / Na and commercial CaAl2O4:Eu / Nd and SrAl2O4:Eu / Dy under the same irradiation conditions, as follows: Figure 6 As shown. Taking the integrated intensity of the afterglow spectrum of CaAl2O4:Eu / Nd as a reference, the afterglow intensity of CaFCl:Eu / Ce / Na is 5.86 times that of CaAl2O4:Eu / Nd and 3.5 times that of SrAl2O4:Eu / Dy. Figure 7 ).

[0038] Comparative Example 1

[0039] The preparation method of CaFCl:Eu in Comparative Example 1 includes the following steps: (1) 10 mmol of calcium fluoride, 9.5 mmol of calcium chloride and 0.5 mmol of europium chloride are mixed and ground evenly in proportion for 60 minutes; (2) The mixture is reacted in a tube furnace for 2 hours at a temperature of 800°C, and a mixture of nitrogen and hydrogen is continuously introduced, with a hydrogen ratio of 5%; (3) After the reaction is completed, the chamber is naturally cooled to room temperature. During the cooling process, a mixture of nitrogen and hydrogen is continuously introduced, with a hydrogen ratio of 5%; (4) The product is kept at 110°C in an oven for 2 hours and cooled to room temperature to obtain CaFCl:Eu afterglow material.

[0040] To further illustrate Ce 3+ and Na + The effect of ion doping on the afterglow properties of CaFCl:Eu was investigated. CaFCl:Eu was prepared under the same conditions. For example... Figure 8 As shown, under the same irradiation and testing conditions, the afterglow decay curve of CaFCl:Eu / Ce / Na is higher than that of CaFCl:Eu, indicating that the afterglow intensity of CaFCl:Eu / Ce / Na is significantly higher than that of CaFCl:Eu under different decay times. The initial afterglow spectral integral intensity of CaFCl:Eu / Ce / Na is 80 times that of CaFCl:Eu. Figure 9 ).

[0041] The luminescence spectrum of CaFCl:Eu / Ce / Na is located in the purple region, which matches the absorption wavelength band of halogen perovskite quantum dots, and the emission wavelength band of halogen perovskite quantum dots can be controlled by changing the components. In order to further prove that the system designed in the application can be used to sensitize halogen perovskite quantum dots, thereby realizing the afterglow spectrum in the full visible light region, first, the CaFCl:Eu / Ce / Na material is made into a flexible transparent film, then halogen perovskite quantum dots with different components are attached to the film, and after the X-ray irradiation stops, the afterglow spectrum of different systems is tested. As shown in Figure 10 Fig. 6, with the change of the components of the quantum dots, the center wavelength of the emission spectrum can gradually extend from 430 nm to 690 nm, realizing the afterglow spectrum control in the full visible light region. This rich afterglow light color can be used for full-color display applications. 0.5 Br 2.5 ,CsPbBr3,CsPbBr1I2,CsPbBr 1.3 I 1.7 ,CsPbBr2I1 and CsPbI3, the center wavelength of the emission spectrum can gradually extend from 430 to 690 nm, realizing the afterglow spectrum control in the full visible light region. This rich afterglow light color can be used for full-color display applications.

Claims

1. An X-ray excited purple rare earth afterglow material with the formula CaFCl:Eu / Ce / Na.

2. The afterglow material according to claim 1, characterized in that CaFCl as a host, divalent rare earth Eu 2+ Ions are the luminescence centers.

3. The afterglow material of claim 1, wherein, Doping with traces of Ce 3+ Ion improves the trap of electrons to Eu 2+ Energy transfer efficiency of the ion, doping with equivalent amounts of Na + Improving the trap concentration while maintaining the charge balance of the system by co-doping with Ce 3+ Co-substitution of Ca 2+ , maintaining the charge balance of the system.

4. The afterglow material of claim 1, wherein, The synergistic effect of the trap concentration improvement and the energy migration efficiency improvement greatly improves the Eu 2+ electron filling efficiency of the ion excited state energy level.

5. The rare earth afterglow material CaFCl:Eu / Ce / Na of claim 1, which is prepared by sequentially comprising the following steps: (1) mixing 10 mmol of calcium fluoride, 9.12-9.93 mmol of calcium chloride, 0.01-0.04 mmol of cerium chloride, 0.05-0.8 mmol of europium chloride, and 0.01-0.04 mmol of sodium chloride in a molar ratio, and grinding them uniformly for 30-60 minutes; (2) reacting the mixture in a tube furnace for 1-3 hours at a temperature of 700-900 °C while continuously supplying a mixed gas of nitrogen and hydrogen with a hydrogen ratio of 5%; (3) after the reaction is completed, naturally cooling to room temperature while continuously supplying the mixed gas of nitrogen and hydrogen with a hydrogen ratio of 5% during the cooling process; (4) maintaining the product in an oven at 80-130 °C for 1-3 hours, and obtaining the CaFCl:Eu / Ce / Na afterglow material after cooling to room temperature.

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