X-ray enhanced luminescent rare earth nanomaterials, preparation method and application thereof

Abstract

The application discloses X-ray enhanced luminescent rare earth nanomaterial and a preparation method and application thereof, and belongs to the field of nanomaterials. The rare earth nanomaterial comprises NaLnF4:Tb rare earth nanoparticles and ligands modified on the surface of the nanoparticles, and the ligands are 2-picolinic acid and the like and are used for passivating surface defects of the nanoparticles. The original oleic acid ligand is replaced by a functional ligand through a simple liquid-phase ligand exchange strategy, the luminescent intensity of the material under X-ray excitation is significantly enhanced under the premise of not changing the size and morphology of the nanoparticles. Compared with the sample modified by oleic acid, the X-ray luminescent intensity of the nanomaterial modified by 2-picolinic acid is increased by about 10 times, the relative light yield can reach 4.68 times of that of a commercial BGO scintillator, and the imaging spatial resolution is as high as 15 lp / mm. The material preparation method is simple, the luminescent efficiency is high, the imaging resolution is excellent, and the material has important application values in the fields of X-ray medical imaging, radiation detection and safety inspection and the like.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of nanomaterials and X-ray luminescence technology, specifically relating to a rare earth nanomaterial with enhanced X-ray luminescence, and more particularly to a rare earth nanomaterial with significantly enhanced X-ray luminescence achieved through ligand modification, its preparation method, and its application in radiation detection and imaging. Background Technology

[0002] X-ray luminescent materials, as important functional materials, have irreplaceable application value in fields such as medical imaging, industrial non-destructive testing, biosensing, and tumor treatment. Rare earth nanoparticles, due to their unique advantages such as high X-ray absorption efficiency, excellent photostability, precisely tunable emission wavelength, easily controlled particle size and morphology, and low biotoxicity, have become a research hotspot for next-generation X-ray luminescent materials, showing broader application prospects compared to traditional inorganic scintillator materials.

[0003] However, key technological bottlenecks remain in the practical application of rare earth nanoparticles in X-ray luminescence: First, the surface of rare earth nanoparticles inevitably contains a large number of structural defects. These surface defects act as luminescence quenching centers, capturing excited-state energy and dissipating it in the form of non-radiative transitions, resulting in a significant reduction in their X-ray luminescence efficiency. Second, traditional long-chain fatty acid ligands such as oleic acid (OA) can only achieve dispersion stability of nanoparticles, but cannot effectively passivate surface defects, making it difficult to solve the luminescence quenching problem. Third, existing technologies cannot simultaneously achieve the "nanoscale" and "high luminescence intensity" characteristics of rare earth nanoparticles, thus failing to meet the practical application requirements of low-dose X-ray detection. Fourth, existing X-ray luminescent rare earth nanoparticles have low detection sensitivity and poor imaging resolution, which cannot meet the practical application requirements of low-dose X-ray detection.

[0004] To address the aforementioned issues, researchers have explored various strategies to enhance the X-ray luminescence performance of rare-earth nanomaterials. For instance, by constructing a core-shell structure to isolate the luminescent center from surface defects, Professor Xu Shiqing's team designed a dual heterogeneous core-shell interface (NaYF4@NaLuF4:Gd / Dy@NaYF4), which enhanced X-ray excited persistent luminescence by approximately 40.9 times and achieved an imaging resolution of 17.1 lp / mm (Lei L, Yi M, Wang Y, et al. Dual heterogeneous interfaces enhance X-ray excited persistent luminescence for low-dose 3Dimaging[J]. Nature Communications, 2024, 15(1).DOI:10.1038 / s41467-024-45390-0.). Furthermore, through ion doping engineering, Ma et al. incorporated Ce...3+ Co-doped NaGdF4:Tb system, using Ce 3+ Electron trapping pathways of ions and Gd 3+ The energy migration-enhanced mechanism of the sublattice significantly reduced afterglow and enabled high-resolution X-ray imaging at 18.6 lp / mm.

[0005] On the other hand, ligand exchange strategies have shown unique advantages in the luminescence regulation of lanthanide nanocrystals. Professors Han Chunmiao and Xu Hui's team modified NaGdF4:Tb nanocrystals with a series of arylphosphine oxycarboxylic acid ligands, promoting rapid intersystem crossing (<1 ns) and efficient triplet energy transfer (up to 96.7%) through strong coupling between the ligands and the nanocrystals, achieving an excellent thin-film photoluminescence quantum yield of 25.55%.

[0006] However, the above technologies still have the following shortcomings: Current methods for enhancing X-ray luminescence mainly rely on high-temperature heat treatment, core-shell structures, or ion co-doping. These methods are complex and primarily focus on controlling bulk defects, lacking systematic research on the precise modification of surface chemical states.

[0007] Although ligand exchange has been used to enhance photoluminescence, X-ray excitation involves complex processes such as high-energy photon-secondary electron cascades, which are significantly different from the photoluminescence mechanism. Currently, there is no rational ligand design specifically for the characteristics of X-ray excitation.

[0008] In summary, although ligand exchange strategies have been widely used to enhance luminescence performance, and replacing functional ligands can effectively improve the surface properties of nanoparticles, their application in X-ray luminescence has not been systematically studied. There is a lack of targeted ligand screening and modification process optimization, and no ligand modification scheme has been developed that can significantly improve X-ray luminescence efficiency. Therefore, developing a rare-earth nanoparticle modification technique that can effectively passivate surface defects of rare-earth nanoparticles, significantly improve X-ray luminescence efficiency, and possess both high detection sensitivity and high imaging resolution has become an urgent technical problem to be solved in this field. Summary of the Invention

[0009] In view of the technical problems of low X-ray luminescence efficiency, severe surface defect quenching, and insufficient detection sensitivity and imaging resolution of rare earth nanoparticles in the prior art, the purpose of this invention is to provide a rare earth nanomaterial that achieves significant enhancement of X-ray luminescence through specific ligand modification.

[0010] To achieve the above objectives, the present invention provides the following technical solution: An X-ray enhanced luminescence rare-earth nanomaterial comprises rare-earth nanoparticles and ligands modified on their surface; the rare-earth nanoparticles are NaLnF4:Tb, where Ln is Gd. 3+ Lu3+ Or Y 3+ The ligand is at least one of a flexible ligand, a neutral conjugated ligand, an electron-donating ligand, or an electron-withdrawing ligand, used to passivate surface defects of the rare earth nanoparticles. Through the coordination interaction between the ligand and the surface of the rare earth nanoparticles, surface defects are effectively passivated, and non-radiative recombination is suppressed, thereby achieving a significant enhancement of X-ray luminescence.

[0011] Preferably, the neutral conjugated ligand can be 2-pyridinecarboxylic acid (2PA) or benzoic acid (BA); the flexible ligand can be acrylic acid (PAA); the electron-donating ligand can be 2-methoxybenzoic acid (2MOBA); and the electron-withdrawing ligand can be 4-nitrobenzoic acid (4NBA), but is not limited thereto.

[0012] Experiments in the embodiments of the present invention have shown that the X-ray luminescence intensity of nanoparticles modified with 2-pyridinecarboxylic acid can be increased by about 10 times compared with that of nanoparticles modified with oleic acid.

[0013] Preferably, the rare earth nanoparticles contain Tb 3+ The doping concentration is 5% to 40%. When Tb 3+ The luminescence intensity reaches its optimal level when the doping concentration is 30%.

[0014] The present invention also provides a method for preparing the above-mentioned rare earth nanomaterials with enhanced X-ray luminescence, comprising the following steps: providing oleic acid-modified NaLnF4:Tb nanoparticles; modifying the surface of the NaLnF4:Tb nanoparticles with ligands through a ligand exchange process to obtain ligand-modified rare earth nanomaterials with enhanced X-ray luminescence.

[0015] The ligand exchange process includes: first, removing the oleic acid from the oleic acid-modified NaLnF4:Tb nanoparticles by acid treatment, then dispersing them in a solvent containing the target ligand after centrifugation for reaction, and finally obtaining a precipitate after centrifugation, which is the ligand-modified NaLnF4:Tb nanoparticles.

[0016] This method is simple, operates under mild conditions, and has good repeatability. Specifically, it includes the following steps: (1) Preparation of OA-coated NaLnF4:Tb nanoparticles: Gadolinium acetate and terbium acetate were mixed in a molar ratio of 7:3, and a mixed solvent of oleic acid and octadecene was added. The mixture was vacuum dried at 150°C to remove moisture and oxygen from the system. After cooling to room temperature, a methanol solution of ammonium fluoride and sodium hydroxide was added, and methanol was removed at 100°C. The temperature was then rapidly increased to 300°C and reacted for 60 min. After the reaction solution cooled naturally, it was centrifuged and washed to obtain OA-coated NaLnF4:Tb nanoparticles.

[0017] (2) Ligand exchange reaction: After centrifugation, the OA-coated NaLnF4:Tb nanoparticles were dispersed in ethanol, and 5.0 mol / L dilute hydrochloric acid was added. The mixture was shaken and centrifuged to obtain ligand-free nanoparticles, which were then dispersed in ethanol. An excess of the target ligand solution was added to the ligand-free nanoparticle solution, and the mixture was sonicated for 5 h. After centrifugation, NaLnF4:Tb nanoparticles with completed ligand exchange were obtained. (3) Purification and drying: Centrifuge the mixture after ligand exchange reaction, collect the precipitate and wash it repeatedly with ethanol 3 to 5 times to remove unreacted excess ligands. Finally, vacuum dry to obtain pure ligand-coated NaLnF4:Tb rare earth nanoparticles.

[0018] This invention further provides the application of the aforementioned ligand-modified rare-earth nanoparticles in the field of X-ray luminescence. Experimental data show that nanoparticles prepared using 2-pyridinecarboxylic acid-modified NaGdF4:Tb achieve a spatial resolution of over 15 lp / mm. The relative light yield of this material is 4.68 times that of commercial scintillator BGO (bismuth germanate), meeting the high-precision requirements of medical diagnostics, biological detection, and other applications.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Significantly improved X-ray luminescence efficiency: The X-ray luminescence intensity of NaGdF4:Tb nanoparticles coated with 2PA is 10 times that of traditional OA coated materials, and the relative light yield is 4.68 times that of BGO crystals, achieving an order-of-magnitude improvement in X-ray luminescence efficiency and solving the core problem of low X-ray luminescence efficiency of rare earth nanoparticles. 2. Highly efficient passivation of surface defects: The 2PA ligand contains both a carboxyl coordination group and a pyridine conjugated ring. The carboxyl group achieves stable binding with the surface of nanoparticles, while the pyridine ring effectively passivates surface defect sites, fundamentally suppressing the luminescence quenching effect caused by surface defects and significantly improving the radiative transition efficiency of excited state energy. 3. High detection sensitivity and imaging resolution: The X-ray emission detection limit of 2PA-coated nanoparticles is as low as 150 nGyair / s, which can achieve high sensitivity detection of low-dose X-rays, and the X-ray imaging resolution reaches 15 lp / mm, which is 3 times that of OA-coated materials, meeting the application requirements of high-resolution imaging. 4. Good stability of luminescence performance: There is a good linear relationship between X-ray luminescence intensity and X-ray dose rate. It exhibits stable luminescence response under different X-ray dose rates. Moreover, the nanoparticles have excellent photostability, can be reused, and are suitable for long-term detection applications. 5. Simple and controllable preparation process: The present invention adopts a ligand exchange strategy for surface modification, with fewer process steps, mild reaction conditions, and simple operation. Moreover, the size, morphology and crystal structure of the nanoparticles remain unchanged after ligand exchange, resulting in good product reproducibility and easy large-scale preparation and industrial production. Attached Figure Description

[0020] Figure 1 This is a transmission electron microscope (TEM) image of the OA-coated NaGdF4:Tb nanoparticles prepared according to the present invention.

[0021] Figure 2 This is a transmission electron microscope (TEM) image of the 2PA-coated NaGdF4:Tb nanoparticles prepared according to the present invention.

[0022] Figure 3 Different Tb prepared according to the present invention 3+ X-ray emission spectra of NaGdF4:Tb nanoparticles coated with a doping concentration of 2PA.

[0023] Figure 4 The X-ray emission spectra of OA-coated NaGdF4:Tb nanoparticles and 2PA-coated NaGdF4:Tb nanoparticles prepared in this invention are shown.

[0024] Figure 5 The X-ray emission spectra of OA-coated NaLuF4:Tb nanoparticles and 2PA-coated NaLuF4:Tb nanoparticles prepared in this invention are shown.

[0025] Figure 6 The X-ray emission spectra of OA-coated NaYF4:Tb nanoparticles and 2PA-coated NaYF4:Tb nanoparticles prepared in this invention are shown.

[0026] Figure 7 The X-ray emission spectra of NaGdF4:Tb nanoparticles coated with different ligands prepared in this invention are shown.

[0027] Figure 8 This paper describes the relationship between the luminescence intensity and dose rate of the 2PA-coated NaGdF4:Tb nanoparticles prepared in this invention under different X-ray dose rates.

[0028] Figure 9 This describes the relative light yield of the 2PA-coated NaGdF4:Tb nanoparticles prepared in this invention.

[0029] Figure 10 This invention relates to the imaging and testing of chips using 2PA-coated NaGdF4:Tb nanoparticles prepared in this invention. Detailed Implementation

[0030] The following examples will further illustrate the content of the present invention. However, these examples do not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0031] Example 1 (1) Preparation of OA-coated NaGdF4:Tb nanoparticles: Weigh 0.7 mmol Gd(CH3CO2)3·6H2O and 0.3 mmol Tb(CH3CO2)3·6H2O and add them to a 50 mL three-necked flask containing 10 mL oleic acid and 15 mL octadecene. The system was dried under vacuum at 150 °C to remove water and oxygen. After cooling to room temperature, 10 mL of methanol solution containing 2 mmol NH4F and 1.6 mmol NaOH was added. The temperature was then raised to 100 °C to remove the methanol solution. The system was then heated to 300 °C under vacuum for 60 minutes. After the reaction, the system was allowed to cool naturally to room temperature. 20 mL of anhydrous ethanol was added to the system, and the mixture was centrifuged at 8000 r / min for 5 minutes to collect the precipitate. The precipitate was washed three times with a cyclohexane-anhydrous ethanol mixture (volume ratio 1:1). Finally, the precipitate was dispersed in cyclohexane to obtain an OA-coated NaGdF4:Tb nanoparticle dispersion. Figure 1 ).

[0032] (2) Preparation of OA-coated NaLuF4:Tb nanoparticles: 0.7 mmol Lu(CH3CO2)3·6H2O and 0.3 mmol Tb(CH3CO2)3·6H2O were weighed and added to a 50 mL three-necked flask containing 10 mL oleic acid and 15 mL octadecene. The system was dried under vacuum at 150 °C to remove water and oxygen. After cooling to room temperature, 10 mL of methanol solution containing 2 mmol NH4F and 1.6 mmol NaOH was added. The temperature was then raised to 100 °C to remove the methanol solution. The system was then heated to 300 °C under vacuum for 60 minutes. After the reaction was completed, the system was allowed to cool to room temperature. 20 mL of anhydrous ethanol was added to the system, and the mixture was centrifuged at 8000 r / min for 5 minutes to collect the precipitate. The precipitate was washed three times with a cyclohexane-anhydrous ethanol mixture (volume ratio 1:1). Finally, the precipitate was dispersed in cyclohexane to obtain an OA-coated NaLuF4:Tb nanoparticle dispersion.

[0033] (3) Preparation of OA-coated NaYF4:Tb nanoparticles: 0.7 mmol Y(CH3CO2)3·6H2O and 0.3 mmol Tb(CH3CO2)3·6H2O were weighed and added to a 50 mL three-necked flask containing 10 mL oleic acid and 15 mL octadecene. The system was dried under vacuum at 150 °C to remove water and oxygen. After cooling to room temperature, 10 mL of methanol solution containing 2 mmol NH4F and 1.6 mmol NaOH was added. The temperature was then raised to 100 °C to remove the methanol solution. The system was then heated to 300 °C under vacuum for 60 minutes. After the reaction was completed, the system was naturally cooled to room temperature. 20 mL of anhydrous ethanol was added to the system, and the mixture was centrifuged at 8000 r / min for 5 minutes to collect the precipitate. The precipitate was washed three times with a cyclohexane-anhydrous ethanol mixed solution (volume ratio 1:1). Finally, the precipitate was dispersed in cyclohexane to obtain an OA-coated NaYF4:Tb nanoparticle dispersion.

[0034] (4) Ligand exchange and purification: Centrifuge 5 mL of the above OA-coated NaGdF4:Tb nanoparticle cyclohexane dispersion, and then redisperse it in 5 mL of ethanol. Add 3.0 mL of 5.0 mol / L dilute hydrochloric acid, shake for a few seconds and centrifuge immediately to obtain ligand-free nanoparticles. Then add 5 mL of 50 mg / mL ethanol solution of the target ligands (2PA, BA, PAA, 2MOBA, 4NBA, respectively) to the ligand-free nanoparticle solution. Sonicate the mixture for 5 hours. After the reaction is complete, centrifuge at 15000 r / min for 15 minutes and collect the precipitate. Wash the precipitate repeatedly with anhydrous ethanol 3 times to completely remove unreacted ligands and other impurities. Place the washed precipitate in a vacuum drying oven at 60℃ and dry for 12 hours to obtain a white solid powder, which is the target ligand-coated NaGdF4:Tb rare earth nanoparticles ( Figure 2 ).

[0035] Following step (4), 2-pyridinecarboxylic acid ligand-coated NaLuF4:Tb and NaYF4:Tb rare earth nanoparticles were also obtained.

[0036] Example 2 To determine Tb 3+ The optimal doping concentration was determined, and Tb was prepared according to the preparation method in Example 1. 3+ NaGdF4:Tb nanoparticles coated with 2PA at doping concentrations of 5%, 10%, 20%, 30%, 40%, and 50% were tested at 20.34 mGy s⁻¹. -1 The X-ray emission intensity of each nanoparticle was measured at the X-ray dose rate. Figure 3 Test results show that when Tb 3+The X-ray emission intensity of the nanoparticles reaches its maximum when the doping concentration is 30%. When the doping concentration is below 30%, the emission intensity increases with increasing doping concentration due to insufficient number of activated ions. When the doping concentration is above 30%, the emission intensity decreases with increasing doping concentration because of concentration quenching, where energy transfer between activated ions leads to increased non-radiative transitions. Therefore, 30% is determined to be the optimal concentration for Tb. 3+ The optimal doping concentration.

[0037] Example 3 (1) X-ray luminescence intensity comparison test: OA-coated nanoparticles and 2PA-coated nanoparticles prepared in Example 1 were compared at 20.34 mGy s⁻¹. -1 The luminescence intensity was measured using an X-ray excitation luminescence testing system at an X-ray dose rate of [value missing]. The results showed that the X-ray luminescence intensity of the 2PA-coated nanoparticles was significantly higher than that of the OA-coated nanoparticles. Specifically, the X-ray luminescence intensity of the 2PA-coated NaGdF4:Tb nanoparticles was 10 times that of the OA-coated nanoparticles. Figure 4-6 ).

[0038] (2) Comparison of X-ray luminescence intensity of different ligand coatings: NaGdF4:Tb nanoparticles coated with OA prepared in Example 1 and NaGdF4:Tb nanoparticles coated with different ligands were compared at 20.34 mGy s⁻¹. -1 At an X-ray dose rate of [value missing], the luminescence intensity was measured using an X-ray excitation luminescence testing system. The results showed that the X-ray luminescence intensity of the nanoparticles after ligand exchange was significantly stronger than that of the original OA-coated nanoparticles. Specifically, the X-ray luminescence intensity of the 2-pyridinecarboxylic acid-coated nanoparticles was 10 times that of the OA-coated nanoparticles. Figure 7 ) (3) Linear relationship test between X-ray luminescence intensity and dose rate: NaGdF4:Tb nanoparticles coated with 2PA were placed at different X-ray dose rates (1.72~20.34 mGy s). -1 X-ray luminescence intensity was measured under [specific conditions], and a curve was plotted with X-ray dose rate on the x-axis and X-ray luminescence intensity on the y-axis. The results showed that [the X-ray luminescence intensity was within the range of 1.72–20.34 mGy / s]. -1 Within the dose rate range, the X-ray emission intensity of the nanoparticles showed a good linear positive correlation with the X-ray dose rate, with a linear correlation coefficient R0. 2 >0.99, exhibiting stable dose-response characteristics ( Figure 8 ).

[0039] (4) Relative light yield test: Using a commercial BGO scintillation crystal as a reference sample, the relative light yield test method was adopted at 20.34 mGy s. -1The relative light yield of 2PA-coated NaGdF4:Tb nanoparticles was tested at a specific X-ray dose rate. The results showed that the relative light yield of these nanoparticles reached 40296 photons MeV. -1 It is 4.68 times that of BGO crystals, exhibiting a far superior X-ray luminescence efficiency compared to traditional scintillation crystals. Figure 9 ).

[0040] Example 4 (1) Imaging resolution test: NaGdF4:Tb nanoparticles coated with OA and NaGdF4:Tb nanoparticles coated with 2PA were prepared into uniform imaging films. An X-ray imager combined with a resolution test plate was used to measure the imaging resolution at 20.34 mGy s⁻¹. -1 The imaging resolution was tested at a specific X-ray dose rate. The results showed that the X-ray imaging resolution of 2PA-coated NaGdF4:Tb nanoparticles reached 15 lp / mm, while the imaging resolution of OA-coated NaGdF4:Tb nanoparticles was only 5 lp / mm. The 2PA ligand modification improved the imaging resolution of the nanoparticles by 2 times.

[0041] (2) Actual sample imaging test: 2PA-coated NaGdF4:Tb nanoparticle dispersion was coated onto the surface of a silicon chip to prepare the sample to be tested, and the image was captured at 20.34 mGy s⁻¹. -1 X-ray imaging tests were conducted at a low X-ray dose rate. The results showed that the nanoparticles could clearly reveal the fine structure of the silicon chip, with high imaging contrast, sharp edges, and no obvious ghosting; under low-dose X-ray conditions (1.72 mGy / s²), the nanoparticles were effectively visualized. -1 It can still obtain clearly identifiable imaging signals, demonstrating good performance in practical applications. Figure 10 ).

Claims

1. A rare-earth nanomaterial with X-ray enhanced luminescence, characterized in that, The rare earth nanomaterial includes rare earth nanoparticles and ligands modified on their surface, the ligands being used to passivate surface defects of the rare earth nanoparticles. The rare earth nanoparticles are NaLnF4:Tb, where Ln is Gd. 3+ Lu 3+ Or Y 3+ ; The ligand is at least one of a neutral conjugated ligand, a flexible ligand, an electron-donating ligand, or an electron-withdrawing ligand.

2. The rare-earth nanomaterial with X-ray enhanced luminescence according to claim 1, characterized in that, The ligand is 2-pyridinecarboxylic acid, benzoic acid, acrylic acid, 2-methoxybenzoic acid, or 4-nitrobenzoic acid.

3. The rare-earth nanomaterial with X-ray enhanced luminescence according to claim 1 or 2, characterized in that, Tb in rare earth nanoparticles 3+ The doping concentration is 5% to 40%.

4. The rare-earth nanomaterial with X-ray enhanced luminescence according to claim 3, characterized in that, Tb in rare earth nanoparticles 3+ The doping concentration is 30%.

5. A method for preparing rare-earth nanomaterials with X-ray enhanced luminescence as described in any one of claims 1-4, characterized in that, Includes the following steps: Oleic acid-modified NaLnF4:Tb nanoparticles are provided; the ligands are modified onto the surface of the NaLnF4:Tb nanoparticles through a ligand exchange process to obtain ligand-modified X-ray enhanced luminescent rare earth nanomaterials.

6. The preparation method according to claim 5, characterized in that, The ligand exchange process includes: first, removing the oleic acid from the oleic acid-modified NaLnF4:Tb nanoparticles by acid treatment, then dispersing them in a solvent containing the target ligand after centrifugation for reaction, and finally obtaining a precipitate after centrifugation, which is the ligand-modified NaLnF4:Tb nanoparticles.

7. An X-ray scintillator, characterized in that, The rare earth nanomaterials comprising X-ray enhanced luminescence as described in any one of claims 1-4, or the rare earth nanomaterials comprising X-ray enhanced luminescence prepared by the method described in claim 5 or 6.

8. An X-ray imaging system, characterized in that, It includes the X-ray scintillator as described in claim 7.

9. The application of a rare earth nanomaterial with X-ray enhanced luminescence as described in any one of claims 1-4, or a rare earth nanomaterial with X-ray enhanced luminescence prepared by the method described in claim 5 or 6, in the fields of radiation detection, medical imaging, or security inspection.

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