High-brightness divalent rare earth afterglow material and delayed X-ray imaging application

Abstract

The invention belongs to the field of rare earth afterglow luminescent materials. The invention discloses a high-brightness divalent rare earth afterglow material. The molecular formula of the high-brightness divalent rare earth afterglow material is BaFCl: Gd / Li / Sm. The preparation method sequentially comprises the following steps: uniformly mixing and grinding barium fluoride, barium chloride, gadolinium chloride, samarium chloride and lithium 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 the product has very strong afterglow performance under X-ray excitation, the afterglow luminescence brightness value can reach 4.53 cd m <-2 >, the afterglow duration is longer than 100 hours, and the product has a very good application prospect in the field of delayed X-ray imaging.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of time-delay X-ray imaging, and relates to a divalent rare earth ion doped fluorochloride material and its application in the field of zero-noise X-ray imaging. BACKGROUND

[0002] The principle of X-ray imaging is based on the difference in density between the physical properties of X-rays and human tissues. By detecting the attenuation changes after X-ray penetration, invisible X-ray photons are converted into visible gray-scale images, thereby reflecting the internal structure of the human body. However, the current X-ray imaging system has two problems. First, the traditional single-crystal scintillator-based X-ray imaging technology usually requires high X-ray radiation dose to obtain high-quality images, which poses a high radiation safety hazard. Second, under continuous X-ray irradiation, the photon signals collected by the X-ray detector device contain not only meaningful transmitted photons but also scattered photons that generate noise points, resulting in a decline in image quality. An effective way to solve the high radiation safety problem is to improve the brightness of the scintillator, thereby reducing the radiation dose without affecting the image quality. The usual method to solve image noise is to add specific optical devices in the imaging equipment or to perform subsequent image processing, but these methods cannot fundamentally remove noise.

[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 in vivo imaging analysis, utilizes the rich energy level structure of rare earth ions, and realizes long afterglow luminescence in the near-infrared two-region under X-ray excitation by doping different rare earth ions, and proves the application prospect of these nanoprobes in the field of deep in vivo tissue imaging. However, the afterglow nanoprobes of this application improve the afterglow performance by constructing a core-shell structure, and the preparation method is a multiple epitaxial growth method, which is complex and not suitable for mass production. Moreover, the afterglow brightness of this system needs to be improved.

[0005] (2) For another example, the invention patent application with the application number 202311466202.0 and the name of an 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 that cannot be perceived by the human eye. The flexible memory film prepared can realize three-dimensional information encryption of curved objects, and the encrypted X-ray image can be safely stored in the film and optically decoded by a layer of perovskite nanocrystals. However, the brightness and afterglow duration of this nanometer ultraviolet afterglow system need to be further improved.

[0006] (3) For example, the authorized invention patent with application number 202410362486.7, entitled "A rare earth element doped phosphate long afterglow material that can only be excited by X-rays and its preparation method and application", can only be excited by X-rays and produce bright green, purple, reddish-brown and orange-red light visible to the naked eye. It cannot be excited by white light and ultraviolet light, so it will not be affected by natural light in daily life. After being irradiated by X-rays for a period of time, it can still be excited by hot water to emit bright green light. It can be used for daily personal and household X-ray dose detection. However, the system is phosphate and is mainly used for radiation dose detection. The afterglow performance also 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, with strong afterglow brightness and long afterglow duration. 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 is mainly used in luminescent devices. The afterglow brightness and duration still need to be improved. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the present invention aims to provide a high-brightness divalent rare-earth afterglow material and its application in time-delayed X-ray imaging. It can produce a bright red afterglow emission after X-ray irradiation, with high afterglow brightness and long duration. It provides a new structural design idea for the development of high-performance rare-earth afterglow materials and fundamentally solves the technical bottleneck of noise generation in real-time X-ray imaging.

[0009] This invention is achieved using the following technical solution: a high-brightness divalent rare-earth afterglow material with the molecular formula BaFCl:Gd / Li / Sm, exhibiting an afterglow luminance value of up to 4.53 cdm. -2 The afterglow lasts for more than 100 hours.

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

[0011] Step 1: Mix and grind 10 mmol of barium fluoride, 8.8-9.7 mmol of barium chloride, 0.1-0.3 mmol of gadolinium chloride, 0.1-0.6 mmol of samarium chloride, and 0.1-0.3 mmol of lithium chloride according to the molar percentage ratio 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 3: After the reaction is complete, allow the chamber to cool naturally to room temperature;

[0014] Step 4: The product is kept in an oven at 100-200℃ for 1-3 hours and then cooled to room temperature to obtain BaFCl:Gd / Li / Sm afterglow material.

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

[0016] 1. A novel structural system with the molecular formula BaFCl:Gd / Li / Sm was constructed through innovative cluster trap design, using BaFCl as the matrix and divalent rare earth element Sm as the substrate. 2+ Gd ions are the luminescent centers. 3+ The role of ions is to introduce localized cluster structures through heterovalent substitution, Li + Its function is to interact with Gd 3+ Together replace Ba 2+ To maintain the charge balance of the system.

[0017] 2. Significantly improved rare-earth afterglow performance: Under X-ray excitation conditions, the afterglow performance was approximately 150 times better than the BaFCl:Sm system, and three times better than the best-performing commercial SrAl2O4:Eu / Dy system. This substantial performance improvement is mainly due to the trap cluster structure significantly enhancing the energy transfer efficiency from the trap electrons to the luminescent center, greatly suppressing energy loss caused by long-distance transmission.

[0018] 3. Using this afterglow material system, a time-delayed flexible X-ray detector was fabricated, achieving low-dose, zero-noise X-ray imaging with a radiation dose of 0.32 μGy / s, which is an order of magnitude lower than the commonly used medical diagnostic value of 5.5 μGy / s.

[0019] 4. This invention proposes to use the afterglow emission generated by X-ray irradiation of a scintillator for imaging, which does not require continuous X-ray irradiation and fundamentally avoids the noise generated by scattered photons. It can realize zero-noise time-delay X-ray imaging and provides a new design idea for developing high-performance X-ray excited rare earth afterglow materials and zero-noise X-ray imaging. Attached Figure Description

[0020] Figure 1 X-ray diffraction pattern of BaFCl:Gd / Li / Sm in Example 1;

[0021] Figure 2 Scanning electron microscope image of BaFCl:Gd / Li / Sm in Example 1;

[0022] Figure 3 Afterglow spectrum of BaFCl:Gd / Li / Sm after X-ray excitation stops in Example 1;

[0023] Figure 4 Afterglow decay curve of BaFCl:Gd / Li / Sm after X-ray excitation stops in Example 1;

[0024] Figure 5 Afterglow spectrum of BaFCl:Gd / Li / Sm 100 hours after X-ray excitation ceases in Example 1;

[0025] Figure 6 In Example 1, the afterglow intensity of BaFCl:Gd / Li / Sm after X-ray excitation cessation is similar to that of Gd. 3+ The relationship curve between ion concentrations, with Gd 3+ The reference ion concentration is 0.4% (molar percentage);

[0026] Figure 7 In Example 1, the afterglow intensity of BaFCl:Gd / Li / Sm after X-ray excitation cessation is compared with that of Sm. 2+ The relationship curve between ion concentration;

[0027] Figure 8 Using the afterglow spectrum test conditions of BaFCl:Gd / Li / Sm in Example 1 as a reference, the afterglow spectrum of commercial SrAl2O4:Eu / Dy was obtained under the same test conditions.

[0028] Figure 9 Example 1: Comparison of the afterglow integral intensity of BaFCl:Gd / Li / Sm with that of commercial SrAl2O4:Eu / Dy, with SrAl2O4:Eu / Dy as a reference;

[0029] Figure 10 Comparison of the afterglow intensity of BaFCl:Sm under X-ray excitation in Comparative Example 1 with that in Example 1, with Comparative Example 1 as a reference.

[0030] Figure 11 Based on the imaging resolution curve of BaFCl:Gd / Li / Sm afterglow luminescence in Example 1;

[0031] Figure 12 Imaging effect diagram of BaFCl:Gd / Li / Sm afterglow luminescence based on Example 1; Detailed Implementation

[0032] The following is combined with Figures 1-12 The present invention will be further described below.

[0033] Example 1

[0034] A high-brightness X-ray excited divalent rare earth afterglow material with the molecular formula BaFCl:Gd / Li / Sm.

[0035] The preparation method of BaFCl:Gd / Li / Sm includes the following steps: (1) 10 mmol of barium fluoride, 9.2 mmol of barium chloride, 0.2 mmol of gadolinium chloride, 0.4 mmol of samarium chloride and 0.2 mmol of lithium chloride are mixed and ground evenly according to the molar percentage 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; (4) The product is kept at 150℃ in an oven for 2 hours and cooled to room temperature to obtain BaFCl:Gd / Li / Sm afterglow material.

[0036] The BaFCl:Gd / Li / Sm 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 Scanning electron microscopy analysis showed that the product had an irregular morphology. Figure 2 After 1 minute of X-ray irradiation, the X-ray source was turned off, and the product exhibited divalent Sm. 2+ The characteristic transition lines include 4f-4f transitions ( Figure 3 The afterglow decay curve indicates that the material exhibits a significant afterglow characteristic, meaning that the luminous intensity gradually decreases over time. Figure 4 ); 100 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 100 hours. Figure 5 ).

[0037] To prove Gd 3+ Ions can enhance afterglow luminescence performance by constructing cluster structures. We compared different Bi ions. 3 + Afterglow properties of samples with high ion concentration. For example... Figure 6 As shown, with Gd 3+ As the ion concentration gradually increased from 0.4% (molar percentage) to 1%, the afterglow luminescence intensity was significantly improved, indicating that Gd doping... 3+ Ions can improve afterglow performance. Gd 3+ Excessive ion doping concentration increases Gd content. 3+ The probability of non-radiative relaxation due to defects leads to a decrease in afterglow performance. This is due to Gd... 3+ The ion is trivalent, and the matrix ion Ba is substituted. 2+ Since Li has a +2 valence, to maintain the charge balance of the system, we introduce a +1 valence Li. + Ions, via Gd 3+ ions and Li + Simultaneously replaces two Ba atoms in the matrix lattice. 2+Gd ions are used to maintain the electroneutrality of the system. Although the entire system is electroneutristic, Gd ions exist within the local microstructures. 3+ Ba in ion-substituted matrix lattice 2+ The ions undergo heterovalent substitution, forming cluster structures within the matrix lattice. Under X-ray irradiation, Frankel defects tend to arise in these cluster structures. In this case, the processes of trapping and releasing electrons are confined within the clusters, significantly suppressing non-radiative losses caused by energy migration within the matrix lattice, thereby substantially increasing the efficiency of the luminescent centers Sm. 2+ The electron filling probability of the excited state energy level is increased, and the afterglow luminescence performance is greatly improved.

[0038] To further optimize the afterglow luminescence performance, we investigated the optimal Sm 2+ Ion doping concentration. For example... Figure 7 As shown, with Sm 2+ As the ion doping concentration gradually increased from 0.5% (molar percentage) to 2%, the afterglow luminescence intensity was significantly improved. 2+ When the ion doping concentration is too high, the afterglow luminescence intensity begins to weaken, indicating that the optimal Sm... 2+ The ion doping concentration is 2%.

[0039] To compare the afterglow performance of this system with the optimal commercial system SrAl2O4:Eu / Dy, we tested the afterglow spectrum of SrAl2O4:Eu / Dy under the same irradiation conditions, as shown below. Figure 8 As shown. Using the integrated intensity of the afterglow spectrum of SrAl₂O₄:Eu / Dy as a reference, the afterglow intensity of BaFCl:Gd / Li / Sm is 3 times that of SrAl₂O₄:Eu / Dy. Figure 9 ).

[0040] Comparative Example 1

[0041] The preparation method of BaFCl:Sm in Comparative Example 1 includes the following steps: (1) 10 mmol of barium fluoride, 9.6 mmol of barium chloride, and 0.4 mmol of samarium chloride are mixed and ground evenly according to the molar percentage 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 mixture is naturally cooled to room temperature; (4) The product is kept at 150°C in an oven for 2 hours and cooled to room temperature to obtain BaFCl:Sm afterglow material.

[0042] To further demonstrate Gd 3+ To investigate the effect of Li+ ion doping on the afterglow performance of BaFCl:Sm, we prepared BaFCl:Sm under the same conditions. Figure 10As shown, under the same irradiation and testing conditions, the afterglow intensity of BaFCl:Gd / Li / Sm is 150 times that of the BaFCl:Sm system.

[0043] To further demonstrate the promising application prospects of the system designed in this invention in the field of time-delay X-ray imaging, we conducted preliminary imaging experiments. For example... Figure 11 As shown, when the modulation transfer function is 0.2, the image resolution can reach 26.1 line pairs / mm, which is superior to commercial flat panel detectors. Figure 12 As shown, the afterglow material prepared using this invention is a flexible thin film, which is wrapped around the surface of a circuit board. After irradiating with X-rays for 1 minute, the film is removed, and the image obtained by the camera clearly shows the internal circuit structure of the circuit board. More importantly, no random white noise appears in the image, which can solve the noise signal caused by scattered X-ray photons in traditional real-time imaging.

Claims

1. A high-brightness divalent rare earth afterglow material with the molecular formula BaFCl:Gd / Li / Sm.

2. The afterglow material according to claim 1, characterized in that, BaFCl is the matrix, Sm 2+ Ions are the luminescent centers, occupying Ba in the matrix. 2+ Dot matrix position.

3. The afterglow material according to claim 1, characterized in that, Through Gd 3+ ions and Li + Simultaneously replaces two Ba atoms in the matrix lattice. 2+ Ions, thereby maintaining the electroneutrality of the system.

4. The afterglow material according to claim 1, characterized in that, Gd was formed in the local microstructure. 3+ Ion clusters greatly suppress radiation-free losses caused by long-distance electron migration and significantly improve afterglow luminescence performance.

5. The rare earth afterglow material BaFCl:Gd / Li / Sm according to claim 1, the preparation process includes the following steps in sequence: (1) 10 mmol of barium fluoride, 8.8-9.7 mmol of barium chloride, 0.1-0.3 mmol of gadolinium chloride, 0.1-0.6 mmol of samarium chloride, and 0.1-0.3 mmol of lithium chloride are mixed and ground evenly according to the molar percentage for 30-60 minutes; (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 a hydrogen ratio of 5%; (3) After the reaction is completed, the chamber is naturally cooled to room temperature; (4) The product is kept at 100-200℃ in an oven for 1-3 hours and cooled to room temperature to obtain the BaFCl:Gd / Li / Sm afterglow material.

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