A long-lasting ultraviolet luminescence material based on X-ray excitation and its application in high-confidential X-ray imaging encryption

Abstract

The present invention relates to the field of X-ray imaging in the field of optical imaging, and specifically to an ultraviolet luminescent long afterglow material based on X-ray excitation, a preparation method and its application in high-confidential X-ray imaging encryption. First, a lanthanide-doped rare earth fluoride nanoscintillator NaLuF 4 Gd 3+ / Ce 3+ Mixed with silica gel to form a thin film, information is stored in the film after X-ray irradiation, and decryption is achieved by coating it with a layer of perovskite and heating it to 80°C. The lanthanide rare earth long-lasting glow nanoparticles studied in this invention exhibit pure ultraviolet luminescence, imperceptible to the naked eye, enabling highly secure X-ray imaging encryption. A flexible memory film made from scintillator nanoparticles enables three-dimensional encryption of curved objects with high resolution and excellent recyclability. Furthermore, encrypted information stored using this technology can be securely stored in the film for seven days and optically decoded using the perovskite.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and specifically relates to an ultraviolet luminescent long afterglow material based on X-ray excitation, a preparation method and its application in high-confidential X-ray imaging encryption. Background Art

[0002] Due to the exceptional penetrating power of X-rays, X-ray imaging has become a key technology in a variety of fields, including clinical medical diagnosis, non-destructive industrial testing, and military applications. In practical applications, X-ray imaging often requires highly secure and large-capacity encrypted storage. Currently, X-ray imaging storage uses traditional methods such as charge-coupled devices (CCDs) and photosensitive or flat-panel imaging plates. However, these technologies may decay rapidly over time or lack the flexibility to store three-dimensional information of irregularly shaped objects. Furthermore, most existing encryption methods allow for multiple decryption attempts, which can lead to information leakage through trial-and-error reading. Despite extensive research, a highly confidential three-dimensional X-ray imaging encryption method has yet to be developed.

[0003] Lanthanide-activated, long-lived scintillators can enable flat-panel-free, high-resolution X-ray imaging. These scintillators possess the ability to trap X-ray energy for extended periods within highly localized Frenkel defects within the lattice, offering opportunities for the development of flexible devices for high-resolution X-ray imaging. However, previously developed scintillators primarily emit light in the visible spectrum. This easy-to-read property carries the risk of leaking stored information. Therefore, synthesizing scintillators with long-term storage capabilities and undetectable luminescence remains a significant challenge. Summary of the Invention

[0004] The present invention aims to provide an ultraviolet luminescent long afterglow material based on X-ray excitation, a preparation method and its application in high-security X-ray imaging encryption technology. 3+ or Ce 3+ X-ray storage devices made of activated nanoscintillators, which have long-lasting, undetectable luminescence, demonstrate high-security X-ray imaging encryption technology; the decryption of high-security X-ray imaging is achieved by energy transfer to the perovskite film.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A long-afterglow ultraviolet luminescence material β-NaLuF4: x% Ln based on X-ray excitation, wherein the material size is 25~300 nm, the crystal phase is (100) hexagonal phase, the Ln is one of Gd or Ce; the x% is the doping amount of doped rare earth ions, and x% is 5%~30%.

[0007] 1. A method for preparing the X-ray-excited ultraviolet luminescence long afterglow material β-NaLuF4:x%Ln as claimed in claim 1, characterized in that it comprises the following steps:

[0008] (1) A rare earth chloride salt is added to a mixed phase solution containing oleic acid and octadecene, and the mixture is vacuum-heated and reacted to obtain a reaction solution;

[0009] (2) After cooling to room temperature, a methanol solution of sodium hydroxide and ammonium fluoride is added to the reaction solution of step (1) to prepare a mixed solution;

[0010] (3) The mixed solution was stirred vigorously and heated at 72°C to evaporate the excess methanol;

[0011] (4) Heating the reaction under vacuum, and then raising the temperature under N2 protection;

[0012] (5) After washing with ethanol and centrifuging, the final product is dispersed in cyclohexane solution for later use.

[0013] Step (1) The rare earth chloride salt is a mixture of LuCl3·6H2O and LnCl3·6H2O; the volume ratio of oleic acid and octadecene in the mixed phase solution is 1:1.5, and the mixing ratio of the rare earth chloride salt to the mixed phase solution is 1:25 mol / L; the vacuum heating temperature is 130°C and the time is 30 min.

[0014] The molar ratio of the sodium hydroxide and ammonium fluoride in step (2) is 1:1.6, the concentration of the methanol solution of sodium hydroxide is 0.25 mol / L, and the concentration of the methanol solution of ammonium fluoride is 0.4 mol / L. The two are mixed and added to the reaction solution of (1); the volume ratio of the methanol-dissolved sodium hydroxide and ammonium fluoride mixed solution to the mixed solution obtained in step (1) is 4:5.

[0015] The stirring temperature in step (3) is 50°C and the stirring time is 30 min.

[0016] In step (4), the vacuum heating temperature is 130°C for 10 min, and the temperature is raised to 300°C for 1 h.

[0017] A method for preparing a high-confidentiality X-ray imaging encryption and decryption device using the ultraviolet luminescent long-afterglow material β-NaLuF4:x% Ln according to claim 1, comprising the following steps: mixing the ultraviolet luminescent long-afterglow material β-NaLuF4:x% Ln with silica gel to prepare a thin film as an information storage film, and decrypting the information with a layer of perovskite after storage.

[0018] The information storage film was prepared by mixing 3 mmol of β-NaLuF4:x% Ln with 0.07 g of silica gel and 1.5 mL of toluene. The mixture was shaken for five minutes and then evenly spread on a PMMA mold on a PET film. The mixture was allowed to stand for 60 minutes and then heated at 60°C for 2 hours to obtain film imaging.

[0019] The information is stored and then decrypted using a layer of perovskite, specifically including the following steps:

[0020] A. Add cesium carbonate to a mixed solution containing oleic acid and octadecene, and heat the mixture under vacuum to react;

[0021] B. heating to obtain a transparent solution; cooling the obtained precursor solution for later use;

[0022] C. PbX2 is added to a mixed solution containing oleic acid, octadecene, and oleylamine, the mixture is heated under vacuum to remove the low-boiling point solvent, and then the temperature is increased to form a transparent solution;

[0023] D. Inject the precursor solution obtained in B and quickly cool it in an ice bath after 10 seconds;

[0024] E. After centrifugation, disperse in cyclohexane for later use.

[0025] In step A, the volume ratio of oleic acid to octadecene in the mixed solution is 1:16, the ratio of cesium carbonate to the mixed solution is 1:17 mol / L, and the vacuum heating temperature is 120° C. for 60 min.

[0026] Step B: heating to 150°C and cooling to 100°C;

[0027] In the PbX2 described in step C, X is one of Cl, Br, and I; in the mixed solution, the volume ratio of oleic acid, oleylamine, and octadecene is 1:1:10; and the mixing ratio of PbX2 to the mixed solution is 0.0317 mol / L.

[0028] The present invention realizes the X-ray imaging encryption mechanism of ultraviolet luminescent long afterglow nanoparticles as follows:

[0029] Pure ultraviolet radiation luminescent scintillator is an ideal material for visually imperceptible X-ray imaging memory. NaLuF4 is used as the matrix because of its low phonon energy, large band gap and high X-ray absorption coefficient, while Gd 3+ and Ce 3+ The ions act as activators to produce an imperceptible luminescent memory of pure ultraviolet radiation.

[0030] Under X-ray excitation, the Frenkel defect center of fluorine is substituted by F -These defects are likely to trap photogenerated charge carriers, as evidenced by the presence of occupied and vacant impurity levels near the valence and conduction band edges. After turning off the X-ray source, the trapped electrons and holes escape during thermal fluctuations and diffuse into the lanthanide activator through the host conduction and valence bands, respectively. Since the occupied 4f orbitals resonate with the host valence band edge, Gd is likely to be formed during hole relaxation. 3+ -hole complexes, which then combine with electron radiation to produce ultraviolet radiation.

[0031] The significant advantages of the present invention are:

[0032] (1) The lanthanide rare earth long afterglow nanoparticles developed by the present invention have pure ultraviolet luminescence that is imperceptible to the naked eye;

[0033] (2) Flexible memory films made of lanthanide-activated nanoparticles can achieve three-dimensional radiographic encryption of curved objects with high spatial resolution and good recyclability;

[0034] (3) Encrypted X-ray images can be securely stored in the membrane for 7 days and optically decoded through a layer of perovskite nanocrystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Electron micrograph of ultraviolet long afterglow nanoparticles excited by X-rays;

[0036] Figure 2 X-ray powder diffraction pattern of ultraviolet long afterglow nanoparticles excited by X-rays;

[0037] Figure 3 X-ray excited ultraviolet long afterglow luminescence image and afterglow characterization;

[0038] Figure 4 From NaLuF4:Gd 3+ Energy transfer from long-lasting nanoparticles to perovskite nanocrystals;

[0039] Figure 5 Schematic diagram of the X-ray imaging encryption writing and decryption reading process;

[0040] Figure 6 Highly confidential flexible X-ray imaging encryption and decryption technology. DETAILED DESCRIPTION

[0041] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the technical solution of the present invention is further explained below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0042] Example 1

[0043] Lanthanide-doped long-lasting glow nanoparticles NaLuF4:Gd 3+ Synthesis of:

[0044] 0.8 mmol LuCl₃ and 0.2 mmol GdCl₃ were added to a 100 mL two-necked round-bottom flask containing 10 mL oleic acid (OA) and 15 mL octadecene (ODE). The mixture was heated to 130°C under vacuum for 30 minutes, forming a clear, transparent solution. After cooling to room temperature, 20 mL of a methanolic solution containing 2.5 mmol sodium hydroxide and 4.0 mmol NH₄F was added to the 130°C solution. The mixture was vigorously stirred at 50°C for 30 minutes and heated at 72°C to evaporate the methanol. The reaction was then continued at 130°C under vacuum for 10 minutes. The temperature was then raised to 300°C and stirred under a nitrogen atmosphere for 1 hour. After cooling to room temperature, the product was washed several times with ethanol and centrifuged. The final product was dispersed in cyclohexane for further use.

[0045] Figure 1 This is the transmission electron microscope (TEM) of X-ray fluorescence nanoparticles. The scale bar in the figure is 100 nm. Figure 1 An obvious hexagonal structure can be seen, and the nanoparticles are evenly distributed and have adjustable sizes. Figure 2 This shows that the X-ray fluorescent nanoparticles have good crystallinity, and their diffraction peak position is consistent with the PDF standard card of NaLuF4 (JCPDS: 27-0726). It has a pure hexagonal phase structure without impurities, which fully demonstrates the successful preparation of long afterglow nanoparticles. Figure 3 The results show that the prepared X-ray excited ultraviolet long afterglow nanoparticles NaLu 0.8 F4:Gd 0.2 It has good X-ray corresponding fluorescence and ultra-long afterglow luminescence performance.

[0046] Example 2

[0047] Construction of visually invisible ultraviolet long afterglow X-ray imaging encryption technology;

[0048] A thin film prepared by mixing the synthesized long-afterglow nano-scintillator with silica gel can be used as an information storage film. After the information is stored, it can be decrypted using a layer of perovskite. The entire device can be used as an X-ray imaging encryption and decryption technology with high confidentiality.

[0049] The long afterglow nanoparticles were embedded in a silica gel mold by adding 3 mmol β-NaLuF4Gd 3+The (20 mol%) nanocrystals were mixed with 0.07 g of silica gel and 1.5 mL of toluene. The mixture was shaken for five minutes and then evenly spread on a PMMA mold on a PET film. After standing for 60 minutes, it was heated at 60°C for 2 hours to obtain a film for imaging.

[0050] Perovskite decryption nanocrystals are prepared as follows:

[0051] A. Add 1.25 mmol of cesium carbonate to 21.25 mL of a mixed solution of oleic acid and octadecene (volume ratio of oleic acid to octadecene:0.0625:1). Heat the mixture at 120°C under vacuum for 60 min.

[0052] B. heating to 150°C to obtain a transparent solution; cooling the obtained precursor solution to 100°C for further use;

[0053] C. Add 0.38 mmol of PbX2 (X is selected from Cl, Br, or I) to a 12 mL mixed solution of oleic acid, oleylamine, and octadecene in a volume ratio of 1:1:10. Heat the mixture at 120°C under vacuum for 30 minutes to remove the low-boiling-point solvent, then heat to 160°C to form a transparent solution.

[0054] D. Inject 0.8 mL of the precursor solution obtained by B and quickly cool it in an ice bath after 10 seconds;

[0055] E. After centrifugation, disperse in cyclohexane for further use.

[0056] During X-ray imaging, the object is placed 5 cm from the X-ray source and excited for 5 minutes, writing the X-ray imaging information into the lanthanide nanoscintillator film. The film is then stored in a -20°C refrigerator. For decryption, a thin layer of perovskite crystals is applied, the resulting film is heated to 80°C, and the associated imaging signals are collected by a camera.

[0057] Figure 4 For NaLuF4Gd 3+ Energy transfer from long-afterglow nanoparticles to perovskite nanocrystals. When the X-ray source is turned off, the hybrid film exhibits multi-color perovskite continuous emission, which shows that there is efficient inter-particle energy transfer from lanthanide nanoscintillators to perovskite nanocrystals. Figure 5 This is a schematic diagram of the X-ray imaging encryption process. It can be seen that neither heating alone nor coating a thin layer of perovskite alone can emit light, indicating that the inventors have achieved effective encryption. Figure 6For the high-confidentiality X-ray imaging encryption and decryption process, it can be seen that the inventors have achieved effective encryption and highly confidential readout of encrypted information. At the same time, the information storage film has high recyclability and photostability, and can realize three-dimensional X-ray imaging of curved objects.

[0058] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. An application of an X-ray-excited ultraviolet luminescent long afterglow material β-NaLuF4:x% Ln in the preparation of a high-confidentiality X-ray imaging encryption and decryption device, characterized in that: A thin film was prepared by mixing the lanthanide-doped rare earth fluoride nanoscintillator β-NaLuF4: x% Ln with silica gel. This film serves as an information storage film. Information is stored in the film after being irradiated with X-rays, and decryption is achieved by coating a layer of perovskite and heating it to 80°C. The Ln is Gd, and the x% is the doping amount of the doped rare earth ion, which ranges from 5% to 30%.

2. The use according to claim 1, characterized in that The specific preparation method of the information storage film includes: mixing 3 mmol of β-NaLuF4:x% Ln with 0.07 g of silica gel and 1.5 mL of toluene, shaking the mixture for five minutes and then evenly spreading it in a PMMA mold on a PET film, letting it stand for 60 minutes and then heating it at 60°C for 2 hours to obtain film imaging.

3. The use according to claim 1, characterized in that The specific method of decryption comprises the following steps: A. Add cesium carbonate to a mixed solution containing oleic acid and octadecene, and heat the mixture under vacuum to react; B. heating to obtain a transparent solution; cooling the obtained precursor solution for later use; C. PbX2 is added to a mixed solution containing oleic acid, octadecene, and oleylamine, the mixture is vacuum-heated to remove the low-boiling point solvent, and then the temperature is raised to form a transparent solution; wherein X is one of Cl, Br, and I; D. Inject the precursor solution obtained in step B and quickly cool in an ice bath after 10 seconds; E. After centrifugation, disperse in cyclohexane for later use.

4. The use according to claim 3, characterized in that In step A, the volume ratio of oleic acid to octadecene in the mixed solution is 1:16, the ratio of cesium carbonate to the mixed solution is 1:17 mol / L, and the vacuum heating temperature is 120° C. for 60 min. Step B: heating to 150°C and cooling to 100°C; In the mixed solution of step C, the volume ratio of oleic acid, oleylamine and octadecene is 1:1:10; the mixing ratio of PbX2 to the mixed solution is 0.0317 mol / L.

5. The use according to claim 1, characterized in that The β-NaLuF4:x% Ln material has a size of 25 to 300 nm and a hexagonal crystal phase.

6. The use according to claim 1, characterized in that The preparation method of β-NaLuF4:x% Ln comprises the following steps: (1) A rare earth chloride salt is added to a mixed phase solution containing oleic acid and octadecene, and the mixture is vacuum-heated and reacted to obtain a reaction solution; (2) After cooling to room temperature, a methanol solution of sodium hydroxide and ammonium fluoride is added to the reaction solution of step (1) to prepare a mixed solution; (3) The mixed solution was stirred vigorously and heated at 72°C to evaporate the excess methanol; (4) Heating the reaction under vacuum, and then raising the temperature under N2 protection; (5) After washing with ethanol and centrifuging, the final product is dispersed in cyclohexane solution for later use.

7. The use according to claim 6, characterized in that The rare earth chloride salt in step (1) is prepared by mixing LuCl3·6H2O and LnCl3·6H2O; the volume ratio of oleic acid and octadecene in the mixed phase solution is 1:1.5, and the mixing ratio of the rare earth chloride salt to the mixed phase solution is 1:25 mol / L; the vacuum heating temperature is 130°C and the time is 30 min.

8. The use according to claim 6, characterized in that The molar ratio of the sodium hydroxide and ammonium fluoride in step (2) is 1:1.6, the concentration of the methanol solution of sodium hydroxide is 0.25 mol / L, and the concentration of the methanol solution of ammonium fluoride is 0.4 mol / L. The two are mixed and added to the reaction solution of step (1); the volume ratio of the methanol-dissolved sodium hydroxide and ammonium fluoride mixture to the mixed solution obtained in step (1) is 4:

5.

9. The use according to claim 6, characterized in that The stirring temperature in step (3) is 50°C and the stirring time is 30 minutes.

10. The use according to claim 6, characterized in that In step (4), the vacuum heating temperature is 130°C for 10 min, and the temperature is raised to 300°C for 1 h.

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