Nanoheterojunction scintillator thin film with x-ray energy resolution function and application thereof

Abstract

The application belongs to the technical field of X-ray detection, and discloses a nano-heterojunction scintillator film with X-ray energy resolution function and application thereof. A composite structure is constructed by combining materials with different X-ray absorption coefficients and scintillation light bands through a heterojunction interface to form a nano-heterojunction scintillator base element. A single nano-heterojunction scintillator base element serves as an independent energy resolution unit and contains at least first-phase and second-phase scintillator materials. The two-phase materials have differentiated X-ray absorption characteristics and light emission characteristics, and are tightly combined through a heterojunction interface. A single-layer scintillation film structure is prepared, and the film is prepared by uniformly dispersing a large number of nano-heterojunction scintillator base elements in an organic matrix. Under X-ray irradiation, the synchronous acquisition of multi-energy channel light signals can be completed through single exposure. The nano-heterojunction scintillator film integrates the energy resolution function in a single nano structure, and can realize the core detection function of the traditional laminated structure relying on a single-layer film, effectively avoiding the problems of interlayer stacking, interface scattering and thickness redundancy existing in the traditional laminated scintillator detector.

Description

Technical Field

[0001] This invention belongs to the field of X-ray detection technology, specifically relating to a nano-heterojunction scintillator thin film with X-ray energy resolution function and its application. Background Technology

[0002] Currently, X-ray detection technology occupies an irreplaceable position in many fields such as industrial non-destructive testing, security inspection, and medical diagnosis. Scintillators, as the core component of X-ray detection, convert high-energy X-rays into low-energy visible light. Most mainstream scintillator detectors currently employ an energy integration detection mechanism, accumulating the total dose of X-rays after penetrating an object to form a grayscale image. However, the X-ray absorption coefficient of different materials strongly depends on the energy of the X-ray photons. Energy integration detection cannot distinguish between X-ray photons of different energies; it can only reflect the overall attenuation difference of the material to X-rays, making it difficult to analyze the energy spectrum information of the material's composition. This inherent physical limitation makes traditional imaging techniques prone to losing crucial information in high-sensitivity, high-resolution imaging scenarios such as early tumor diagnosis, composite material composition analysis, and precise identification of hazardous materials.

[0003] Energy-resolved X-ray detection technology analyzes the energy of X-rays penetrating an object, revealing its internal information in a multi-dimensional and more precise manner. Currently, mainstream energy-resolved detection technologies rely on photon counting detectors, but these suffer from problems such as photon stacking effects, difficulties in fabricating high-quality detector crystals, and challenges in achieving large-area imaging. In recent years, an alternative approach has emerged: stacked scintillator detectors. This involves stacking multiple layers of scintillators with different absorption characteristics and emission bands for X-rays of different energies, encoding energy information into spectral information to achieve energy-resolved detection in a single exposure. However, this stacked structure has the following inherent drawbacks: First, due to limitations imposed by interlayer stacking, interface scattering, and thickness redundancy, significant light reflection and scattering exist between layers, leading to a reduction in the number of detected photons and decreased detection efficiency. Second, ensuring high transmittance of the bottom scintillator to the top layer requires complex thin-film fabrication and coupling processes, increasing system design and manufacturing costs. Third, the method of mechanically mixing multiple scintillators on a single-layer film to simplify the structure makes it difficult to guarantee component homogeneity, easily leading to segregation and causing the energy-resolved model to fail.

[0004] Therefore, there is an urgent need to develop a new energy-resolved X-ray detection technology that can overcome the defects of stacked structures and achieve high efficiency, uniformity, and ease of fabrication. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the aforementioned stacked scintillator detectors by proposing an effective method for achieving a new generation of energy-resolved X-ray detection technology that combines energy spectrum discrimination and material differentiation. Specifically, it is a nano-heterojunction scintillator film with X-ray energy resolution function. The nano-heterojunction scintillator film has outstanding advantages in the fabrication of X-ray detection equipment, enabling energy resolution function and featuring a simple structure that is easy to integrate.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a nano-heterojunction scintillator thin film with X-ray energy resolution capability, wherein the nano-heterojunction scintillator thin film is a single-layer scintillator thin film structure, such as... Figure 1As shown, the thin film contains a large number of nano-heterojunction scintillator units uniformly dispersed in an organic matrix; each nano-heterojunction scintillator unit, as an independent energy-resolving unit, is formed by N-phase scintillators bonded together through a heterojunction interface, where N≥2; the X-ray energy spectrum adapted to the N-phase heterojunction scintillators is divided into N energy bands, and the absorption capacity of different phase scintillators for X-rays varies; the materials of the N-phase scintillators are different from each other, and are labeled as phase 1, phase 2... phase N in order of increasing X-ray absorption capacity. The absorption efficiency of each phase scintillator in different energy bands is controlled by optimizing the geometric parameters of the nanostructure, i.e., the equivalent thickness; for any nth phase scintillator (1≤n≤N). By combining the Lambert-Beer law with the absorption coefficient curves of the nth phase scintillator material for X-rays of different energies, its geometric parameters are determined to ensure that the nth phase scintillator preferentially absorbs X-rays in the first n energy ranges, with the absorption of X-rays in the first n energy ranges accounting for more than 60% of the total X-ray energy absorbed by this phase scintillator. Specifically, the absorption of X-rays in the nth energy range accounts for no less than 20%, and the absorption of X-rays in the n-1th phase scintillator in the nth energy range does not exceed 50% of the absorption of X-rays in that energy range by the nth phase scintillator. In the N-phase heterojunction scintillator, the emission spectra of each phase material must have sufficient distinguishability, i.e., the difference in the spectral emission center wavelength of the scintillator emitted by any two phases is no less than 100 nm. nm, and the area of ​​mutual overlap between the two spectra is less than 20% of the total area of ​​their respective scintillation spectra, to ensure that the corresponding spectral information can be effectively extracted from the final detection data; the organic matrix is ​​any one of polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl toluene (PVT), thermoplastic polyurethane (TPU), polypropylene (PP), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), epoxy resin, cellulose acetate (CA), polyethersulfone (PES), polyimide (PI), polylactic acid (PLA), polycaprolactone (PCL), unsaturated polyester resin, phenolic resin, photocurable acrylic resin, silicone rubber, and urea-formaldehyde resin. As a further preferred embodiment of the first aspect above, N is preferably 2 to 4.

[0008] As a further preferred embodiment of the first aspect above, the geometric configuration of the nano-heterojunction scintillator unit includes, but is not limited to, a cube, a sphere, or a rod, and the heterojunction type is not limited to a core-shell structure or an end-to-end structure.

[0009] As a further preferred embodiment of the first aspect, in the N-phase heterojunction scintillator, the emission spectra of each phase material need to have sufficient distinguishability, so that a non-interacting inert isolation layer can be introduced between any two phases to form a physical barrier to carrier migration and effectively suppress energy transfer.

[0010] As a further preferred embodiment of any of the above-mentioned first aspect, N=2, the heterojunction is a core-shell structure, and from the outside to the inside, the first phase scintillator material is CsMn(Cl / Br)3 with an equivalent thickness of 20 μm; it mainly absorbs low-energy X-rays (0~20 keV) and emits red scintillator light; the second phase scintillator material is CsPb(Cl / Br)3 with an equivalent thickness of 100 μm, which not only absorbs low-energy (0~20 keV) but also absorbs high-energy X-rays (20~40 keV), emitting blue scintillator light. The emission peak center wavelengths of the core-shell scintillators are 433 nm and 604 nm, respectively, with a wavelength difference greater than 100 nm, and their spectra do not overlap.

[0011] As a further preferred embodiment of any of the above-mentioned first aspect, N=2, the heterojunction is a core-shell structure, and from the outside to the inside, the first phase scintillator material is NaYF4:Tb with an equivalent thickness of 15μm; it mainly absorbs low-energy X-rays (0~20keV) and emits green scintillator light; the second phase scintillator material is NaLuF4:Yb with an equivalent thickness of 100 μm; it can absorb both low-energy and high-energy ranges (0~40keV) and emits near-infrared scintillator light. The center wavelengths of the core-shell scintillators are 545 nm and 980 nm, respectively, with a wavelength difference greater than 100 nm, and their spectra do not overlap. There is a layer of NaYF4 between the first and second phase scintillator materials as an inert isolation layer to prevent energy transfer between the innermost and outermost layers.

[0012] Secondly, the present invention provides a method for preparing the above-mentioned nano-heterojunction scintillator thin film, the method comprising the following steps:

[0013] Step S1, Preparation of nano-heterojunctions: Using a wet chemical method, by controlling the thermodynamic and kinetic parameters such as the ratio of raw materials, reaction solvent, surfactant, and reaction temperature and time, nano-heterojunctions with X-ray absorption gradient and multiphase synergistic luminescence characteristics are prepared.

[0014] Step S2, Preparation of scintillator film: The nano-heterojunction powder or dispersion prepared in step S1 is mixed with the above-mentioned organic matrix, and a uniformly distributed scintillator film is prepared by means of scraping, printing or pressure molding process.

[0015] The core-shell heterojunction nanocrystals obtained by the above preparation method have excellent solution processability and can be easily prepared to form a single-layer scintillator screen with high light transmittance, avoiding problems such as interlayer stacking, interface scattering and thickness redundancy in traditional stacked scintillators, thus providing an efficient and feasible technical strategy for multi-energy spectral imaging.

[0016] Thirdly, the present invention provides the application of the above-mentioned nano-heterojunction scintillator thin film in the fabrication of X-ray detection equipment, namely, providing an energy-resolved X-ray detection equipment, the energy-resolved X-ray detection equipment including an X-ray source, the above-mentioned heterojunction scintillator thin film and a spectral information collection module; the above-mentioned heterojunction scintillator thin film is the nano-heterojunction scintillator thin film described in either the first aspect or the second aspect; the spectral information collection module is disposed directly below the nano-heterojunction scintillator detector and is used to collect scintillation information of different wavelengths emitted by each phase scintillator.

[0017] Compared with existing technologies, this invention has the following advantages: It integrates energy-resolution functionality into a single nano-heterojunction unit, achieving the core detection function of traditional multilayer structures with a single-layer thin film, effectively avoiding problems such as interlayer stacking, interface scattering, and thickness redundancy inherent in traditional multilayer scintillator detectors. No complex multilayer coupling process is required; only a single-layer scintillator screen needs to be fabricated, greatly simplifying system design and manufacturing. Simultaneously, the structural characteristics of the nano-heterojunction ensure uniform component distribution, and the heterojunction nanocrystals possess excellent solution processability, allowing for the easy fabrication of high-transmittance single-layer scintillator screens. Furthermore, this energy-resolution scintillator thin film has the potential for large-area array fabrication and is highly compatible with existing mature silicon-based detection technologies. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the energy-resolution detection function achieved by utilizing a nano-heterojunction scintillator thin film according to the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the metal halide two-phase nano-heterojunction scintillator in Example 1;

[0020] Figure 3 The image shows the morphology of the nucleus in the metal halide two-phase nanoheterojunction scintillator in Example 1.

[0021] Figure 4 This is a morphological characterization diagram of the core and shell in the metal halide two-phase nano-heterojunction scintillator in Example 1;

[0022] Figure 5 This is an absorption diagram of X-rays of different energies by the two-phase scintillator in the metal halide two-phase nanoheterojunction scintillator of Example 1.

[0023] Figure 6 The image shows the scintillation spectrum of the two-phase scintillator in the metal halide two-phase nanoheterojunction scintillator of Example 1.

[0024] Figure 7 Material-energy correlation calibration curves for copper (Cu), zinc (Zn), and polymethyl methacrylate (PMMA) in Example 1;

[0025] Figure 8 This is a schematic diagram of the structure of the rare earth fluoride two-phase nanoheterojunction scintillator in Example 2;

[0026] Figure 9 The image shows the morphology of the nucleus in the rare earth fluoride two-phase nanoheterojunction scintillator in Example 2.

[0027] Figure 10 This is a morphological characterization diagram of the core and shell in the rare earth fluoride two-phase nano-heterojunction scintillator in Example 2;

[0028] Figure 11 This is an absorption diagram of X-rays of different energies in the rare earth fluoride two-phase nanoheterojunction scintillator in Example 2.

[0029] Figure 12 The image shows the scintillation spectrum of the two-phase scintillator of the rare earth fluoride two-phase nanoheterojunction scintillator in Example 2.

[0030] Figure 13 The material-energy correlation calibration curves for tin (Sn), aluminum (Al) and polymethyl methacrylate (PMMA) in Example 2 are shown. Detailed Implementation

[0031] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the invention are all within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0032] The main raw materials and equipment models involved in the following examples are shown below:

[0033] The X-ray tube model is Amptek Mini-X2, W target, with a tube voltage of 35-70 kV and a tube current of 5-200 µA.

[0034] The transmission electron microscope is a Hitachi HT7700.

[0035] Example 1: Preparation and Energy Resolution Characteristics Study of Metal Halide Two-Phase Nanostructured Scintillator Thin Films

[0036] 1. Material selection:

[0037] Two different materials are selected as the two phases of the nanoheterostructure. The first phase absorbs only low-energy X-rays, while the second phase absorbs both low-energy and high-energy X-rays. By subtraction, the absorption of high-energy X-rays by the second phase can be separated, thus distinguishing the absorption information of low-energy and high-energy X-rays. Figure 2As shown, the two-phase nano-heterojunction has a core-shell structure. From the outside to the inside, the first phase scintillator material is CsMn(Cl / Br)3, which mainly absorbs low-energy X-rays (0~20keV) and emits red scintillating light. The second phase scintillator material is CsPb(Cl / Br)3, which not only absorbs low-energy X-rays (0~20keV) but also absorbs high-energy X-rays (20~40keV) and emits blue scintillating light.

[0038] 2. Preparation of nanoheterostructures:

[0039] 1) Preparation of nuclear nanocrystals: 0.15 mmol of lead bromide (PbBr2), 0.0378 mmol of lead chloride (PbCl2), 5 ml of octadecene (ODE), 0.5 ml of oleic acid (OA), and 0.5 ml of oleylamine (OAm) were added to a 50 ml three-necked flask. The mixture was heated to 120 °C under vacuum and stirred for 1 hour. Under a N2 atmosphere, the temperature was further increased to 155 °C, and 0.4 ml of cesium oleate was immediately injected. After reacting for 5 seconds, the reaction was immediately quenched in an ice-water bath. Subsequently, the reaction product was washed and centrifuged multiple times with pure toluene solvent. The final reaction product was dispersed in 1 mL of n-hexane to obtain a nuclear nanocrystal dispersion for later use.

[0040] 2) Preparation of core-shell heterojunction nanocrystals: 0.125 mmol of manganese chloride (MnCl2), 0.0075 mmol of manganese bromide (MnBr2), 5 ml of ODE, 0.5 ml of OA, and 0.5 ml of OAm were added to a 50 ml three-necked flask. The mixture was heated to 120 °C under vacuum and stirred for 1 h. The core nanocrystal dispersion was then injected into the flask under N2 atmosphere. The mixture was evacuated for 10 min and heated to 150 °C under N2 atmosphere. Immediately afterward, 0.4 ml of cesium oleate was injected. After reacting for 5 s, the reaction was quenched immediately with an ice-water bath. Subsequently, the reaction product was washed and centrifuged multiple times with pure toluene solvent to obtain core-shell heterojunction nanocrystal powder.

[0041] 3) Preparation of core-shell heterojunction nanocrystalline scintillator film: Polymethyl methacrylate (PMMA) was dissolved in toluene solution and stirred continuously at 60°C until the solution became clear and transparent. The core-shell nanocrystalline heterojunction powder obtained in step 2 was added to the above-dissolved transparent solution and heated and stirred for more than 6 hours to ensure that the scintillator powder was uniformly dispersed in the solution. The above mixture was rapidly drop-coated onto a clean glass plate using a dropper method, and a petri dish was inverted on the surface of the glass plate to effectively control the evaporation rate of toluene. After standing for more than 8 hours, the film was peeled off the glass plate with tweezers.

[0042] All of the above operations must be performed inside a fume hood to ensure safety.

[0043] 3. Particle morphology analysis:

[0044] TEM images were obtained using a transmission electron microscope (TEM, Hitachi HT7700) at magnifications ranging from ×200 to ×200,000, with accelerating voltages ranging from 40 to 120 kV. The operating voltage during imaging was set to 100 kV. By controlling the ratio of the two phases, core-shell heterostructure nanocrystals CsPb(Cl / Br)3 / CsMn(Cl / Br)3 with relatively uniform morphology were successfully prepared. (See reference...) Figure 3 , Figure 4 The figure shown is a TEM morphology characterization image of the core and core-shell prepared in Example 1.

[0045] 4. X-ray absorption calculation and analysis:

[0046] The X-ray attenuation efficiency (AE) of the scintillator is calculated using the following formula.

[0047] ;

[0048] Where AE represents the X-ray attenuation efficiency (in %) of the scintillator within a specific thickness and X-ray photon energy range. c(ε) is the X-ray mass absorption coefficient obtained from the XCOM database of the National Institute of Standards and Technology (NIST), ρ is the density of the scintillator material, and d is the thickness of the scintillator film. The X-ray source operates at a voltage of 50 kV, and the X-ray energy spectrum mainly covers the range of 0–40 keV, which is divided into two equal energy ranges: the first energy range (0–20 keV) and the second energy range (20–40 keV). Figure 5 As shown, the absorption of X-rays by the first phase CsMn(Cl / Br)3 and the second phase CsPb(Cl / Br)3 exhibits significant differences. The absorption of X-rays in the first energy range by the first phase scintillator accounts for 86% of the total energy absorbed by that phase. The absorption of X-rays in both the first and second energy ranges by the second phase scintillator is equal to the total energy absorbed by that phase, both satisfying the condition of not less than 60%. Specifically, the absorption of X-rays in the second energy range by the second phase scintillator accounts for 40%, satisfying the condition of not less than 20%. The absorption of X-rays in the second energy range by the first phase scintillator is 13% of the absorption of X-rays in the second energy range by the second phase scintillator, satisfying the condition of not more than 50%.

[0049] 5. Characterization and analysis of radiative luminescence properties:

[0050] The emission spectrum under X-ray excitation was obtained by using an X-ray tube as the excitation source, placing the scintillator under test between the X-ray tube and the receiving detector, and recording the emission spectrum under X-ray excitation using a marine optical spectrometer. The entire experiment was conducted in a lead box. The scintillation spectra of the first and second phase materials are as follows: Figure 6As shown, these originate from exciton transitions in CsPb(Cl / Br)3 and Mn, respectively. 2+ of 4 T1→ 6 The A1 transition has center wavelengths of 433 nm and 604 nm, respectively, satisfying that the difference in center wavelength of the emission peaks of any two phase scintillators is not less than 100 nm; and that the two spectra do not overlap, satisfying that the ratio of the overlapping area of ​​the two phase spectra is less than 20%.

[0051] 6. Energy resolution characteristic analysis:

[0052] Three materials were selected for testing: polymethyl methacrylate (PMMA), copper (Cu), and zinc (Zn). These materials were placed between an X-ray source and the scintillator film prepared in Example 1. By adjusting the X-ray source voltage / current parameters—operating voltage of 50 kV and operating current of 140 µA—a broad-spectrum X-ray beam was generated. The characteristic wavelength emission signals of each energy channel of the scintillator film were simultaneously acquired, and the integrated area of ​​each energy channel (red and blue light channels) was calculated. After further collecting data on different thicknesses of each material, material-energy dependence calibration curves were obtained. Figure 7 As shown, it is obvious that the three materials exhibit clear distinguishing boundaries, which can serve as the basis for classifying and identifying different materials.

[0053] Example 2: Preparation and Energy Resolution Characteristics Study of Rare Earth Fluoride Two-Phase Nanostructured Scintillator Thin Films

[0054] 1. Material selection:

[0055] like Figure 8 As shown, the two-phase heterojunction in Example 2 has a core-shell structure. From the outside to the inside, the first-phase scintillator material is NaYF4:Tb with an equivalent thickness of 15 μm; it mainly absorbs low-energy X-rays (0~20 keV) and emits green scintillator light. The second-phase scintillator material is NaLuF4:Yb with an equivalent thickness of 100 μm; it can absorb both low-energy and high-energy ranges (0~40 keV) and emits near-infrared scintillator light. The center wavelengths of the core-shell scintillators are 545 nm and 980 nm, respectively, with a wavelength difference greater than 100 nm, and their spectra do not overlap. There is a layer of NaYF4 between the first-phase and second-phase scintillator materials, which acts as an inert isolation layer to prevent energy transfer between the innermost and outermost layers.

[0056] 2. Material synthesis method:

[0057] 1) Preparation of NaLuF4:Yb core nanocrystals: 0.76 mmol of lutetium(III) chloride hexahydrate (LuCl3·6H2O), 0.04 mmol of ytterbium(III) chloride hexahydrate (YbCl3·6H2O), and 8 ml of OA were added to a 50 ml three-necked flask. The mixture was heated to 150 °C and held for 30 min under a nitrogen atmosphere. 12 ml of ODE was injected using a syringe, and the reaction was allowed to proceed for 30 min to obtain a clear and transparent solution. The solution was then cooled to room temperature. 2 mmol of sodium hydroxide (NaOH) and 3 mmol of ammonium fluoride (NH4F) were weighed and dissolved in 10 ml of methanol. The methanol mixture was slowly added dropwise to the three-necked flask, and the mixture was heated to 80 °C and held for 1 h to remove methanol. A condenser was then installed, and the temperature was raised to 150 °C and held for 10 min. The mixture was then rapidly heated to 280 °C and held for 90 min. Finally, cool the mixture to room temperature. Place the reaction solution in a centrifuge tube, add a small amount of ethanol to wash and allow it to separate into layers. Centrifuge to remove the supernatant and collect the precipitate. Repeat the above steps, and finally store the powder in 2 ml of cyclohexane in a refrigerator.

[0058] 2) Preparation of NaLuF4:Yb / NaYF4 core-shell nanocrystals: This step involves coating the first phase, NaLuF4:Yb, with an intermediate inert layer, NaYF4. 0.8 mmol of YCl3·6H2O and 8 ml of OA were added to a 50 ml three-necked flask. The mixture was heated to 150 °C and held for 30 min under a nitrogen atmosphere. 12 ml of ODE was injected using a syringe, and the reaction was allowed to proceed for 30 min, yielding a clear and transparent solution. The solution was then cooled to 70 °C. NaLuF4:Yb nanoparticles dispersed in cyclohexane were added, and the mixture was heated to 100 °C and held for 40 min to remove the cyclohexane. The mixture was then cooled to room temperature. 2 mmol of NaOH and 3 mmol of NH4F were dissolved in 10 ml of methanol. The methanol mixture was slowly added dropwise to the three-necked flask, and the mixture was then heated to 80 °C and held for 1 h. Replace the condenser sleeve, heat to 150℃ and hold for 10 min, then rapidly heat the mixed solution to 280℃ and hold for 90 min. Finally, cool the mixture to room temperature; the post-treatment process is the same as in the preparation of NaLuF4:5%Yb.

[0059] 3) Preparation of NaLuF4:5%Yb / NaYF4 / NaYF4:10%Tb core-shell nanocrystals: The synthesis method is the same as that for NaLuF4:5%Yb / NaYF4, except that the initial raw materials are replaced with 0.72 mmol of YCl3·6H2O and 0.08 mmol of TbCl3·6H2O. The post-processing is the same as that for the preparation of NaLuF4:5%Yb, thus obtaining the scintillator material NaLuF4:5%Yb / NaYF4 / NaYF4:10%Tb of Example 2.

[0060] 4) Preparation of core-shell heterojunction nanocrystalline thin films: PMMA was dissolved in toluene solution and stirred continuously at 60°C until the solution became clear and transparent. The scintillator obtained above was added to the dissolved transparent solution and heated and stirred for more than 6 hours to ensure uniform dispersion of the mixed solution. The mixture was rapidly drop-coated onto a clean glass plate using a drop-drop method, and a petri dish was inverted on the surface of the glass plate to effectively control the evaporation rate of toluene. After standing for more than 8 hours, the film was peeled off the glass plate with tweezers.

[0061] Note that all the above operations must be performed inside a fume hood to ensure safety.

[0062] 3. Particle morphology analysis:

[0063] TEM images were obtained using a transmission electron microscope (TEM, Hitachi HT7700) with magnifications ranging from ×200 to ×200,000 and accelerating voltages from 40 to 120 kV. The operating voltage during imaging was set to 100 kV. Figure 9 , Figure 10 As shown, it can be seen that the NaLuF4:Yb core and the NaLuF4:Yb / NaYF4 / NaYF4:Tb core-shell are heterogeneous nanocrystals with uniform morphology.

[0064] 4. X-ray absorption calculation and analysis: The same X-ray absorption calculation and analysis steps as in Example 1 are used.

[0065] like Figure 11 As shown, the absorption of X-rays by the first phase NaYF4:Tb and the second phase NaLuF4:Yb exhibits significant differences. The first phase scintillator absorbs 80% of the total energy absorbed by the first energy band of X-rays. The absorption of the first and second energy bands of X-rays by the second phase scintillator is equal to the total energy absorbed by the phase (both satisfying the condition of not less than 60%). Specifically, the absorption of the second energy band of X-rays by the second phase scintillator accounts for 38% (satisfying the condition of not less than 20%). The absorption of the second energy band of X-rays by the first phase scintillator is 15% of the absorption of the second energy band of X-rays by the second phase scintillator (satisfying the condition of not more than 50%).

[0066] 5. Characterization and analysis of radiative luminescence properties:

[0067] Using the same spectral testing method as in Example 1, the scintillation spectra of the first and second phase materials are as follows: Figure 12 As shown, the Tb range is 480nm~700nm. 3+ The light emission peak, with the highest intensity, is located at 545 nm and originates from Tb. 3+ of 5 D4 → 7 F5 transition; the peak with a center wavelength of 980nm originates from Yb 3+ of 2 F 5 / 2 → 2 F 7 / 2 Leap, such as Figure 12 As shown, the spectra of the two phases do not overlap, satisfying the condition that the ratio of the overlapping area of ​​the two phase spectra is less than 20%.

[0068] 6. Energy resolution characteristic analysis: The operation steps and calculation methods are the same as in Implementation 1 above. For example... Figure 13 As shown, the material-energy dependence calibration curves clearly show that the three materials exhibit distinct boundaries, which can serve as the basis for classifying and identifying different materials.

Claims

1. A nanostructured heterojunction scintillator thin film with X-ray energy resolution capability, characterized in that, The nano-heterojunction scintillator film is a single-layer scintillator film structure. The scintillator film contains nano-heterojunction scintillator units uniformly dispersed in an organic matrix. Each scintillator unit is formed by N-phase scintillators bonded together through a heterojunction interface, where N ≥ 2. The X-ray energy spectrum adapted to the N-phase heterojunction scintillator is divided into N equal energy segments. The N-phase scintillators are labeled sequentially from weakest to strongest X-ray absorption capacity as phase 1, phase 2, ..., phase N. For any nth phase scintillator, 1 ≤ n ≤ N, the Lambert-Beer law, combined with the material properties of the nth phase scintillator, is used to determine the absorption capacity of different phases of the scintillator. The absorption coefficient curves of X-rays of the same energy are calculated to determine their geometric parameters, so that the nth phase scintillator preferentially absorbs X-rays of the first n energy ranges, with the absorption of X-rays of the first n energy ranges accounting for more than 60% of the total X-ray energy absorbed by the phase scintillator, of which the absorption of X-rays of the nth energy range accounts for no less than 20%, and the absorption of X-rays of the nth energy range by the (n-1)th phase scintillator does not exceed 50% of the absorption of X-rays of the nth energy range by the nth phase scintillator; in the N-phase heterojunction scintillator, the difference in the spectral emission center wavelength of the scintillating light emitted by any two phases is not less than 100 nm. nm, and the area of ​​mutual overlap of the two spectra is less than 20% of the total area of ​​their respective scintillation spectra; the organic matrix is ​​any one of polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl toluene (PVT), thermoplastic polyurethane (TPU), polypropylene (PP), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), epoxy resin, cellulose acetate (CA), polyethersulfone (PES), polyimide (PI), polylactic acid (PLA), polycaprolactone (PCL), unsaturated polyester resin, phenolic resin, photocurable acrylic resin, silicone rubber, and urea-formaldehyde resin.

2. The nano-heterojunction scintillator thin film as described in claim 1, characterized in that, The value of N is 2 to 4.

3. The nano-heterojunction scintillator thin film as described in claim 1, characterized in that, The geometry of the nanoheterojunction scintillator unit includes cubes, spheres, or rods.

4. The nano-heterojunction scintillator thin film as described in claim 1, characterized in that, The heterojunction types of the nano-heterojunction scintillator unit include core-shell structure and end-to-end structure.

5. The nano-heterojunction scintillator thin film as described in claim 1, characterized in that, With N=2, the nano-heterostructure is a core-shell structure. From the outside to the inside, the first phase scintillator material is CsMn(Cl / Br)3 with an equivalent thickness of 20 μm. It mainly absorbs low-energy X-rays of 0~20 keV and emits red scintillating light. The second phase scintillator material is CsPb(Cl / Br)3 with an equivalent thickness of 100 μm. It not only absorbs low-energy X-rays of 0~20 keV but also absorbs high-energy X-rays of 20~40 keV and emits blue scintillating light. The center wavelengths of the emission peaks of the core-shell scintillators are 433 nm and 604 nm, respectively, with a wavelength difference greater than 100 nm. The spectra of the two scintillators do not overlap.

6. The nano-heterojunction scintillator thin film as described in claim 1, characterized in that, In the N-phase heterojunction scintillator, a non-interacting inert isolation layer is also provided between any two phases.

7. The nano-heterojunction scintillator thin film as described in claim 6, characterized in that, N=2. The nano-heterostructure is a core-shell structure. From the outside to the inside, the first phase scintillator material is NaYF4:Tb with an equivalent thickness of 15μm. It mainly absorbs low-energy X-rays of 0~20keV and emits green scintillating light. The second phase scintillator material is NaLuF4:Yb with an equivalent thickness of 100μm. It can absorb low-energy and high-energy ranges of 20~40keV and emits near-infrared scintillating light. The center wavelengths of the core-shell scintillators are 545nm and 980nm, respectively, with a wavelength difference greater than 100nm, and their spectra do not overlap. The inert isolation layer between the first and second phase scintillator materials is NaYF4.

8. The method for preparing a nano-heterojunction scintillator thin film according to claim 1, characterized in that, The preparation method includes the following steps: using a wet chemical method, by controlling thermodynamic and kinetic parameters, a nano-heterojunction with X-ray absorption gradient and multiphase synergistic luminescence characteristics is prepared; the prepared nano-heterojunction powder or dispersion is mixed with the organic matrix, and a uniformly distributed scintillator film is prepared by using a scraping, printing or pressure molding process.

9. The application of the nano-heterojunction scintillator thin film as described in claim 1 in the fabrication of X-ray detection equipment.

10. An energy-resolved X-ray detection device, the energy-resolved X-ray detection device comprising an X-ray source, a heterojunction scintillator thin film, and a spectral information collection module, characterized in that, The heterojunction scintillator film is the nano-heterojunction scintillator film according to claim 1; the spectral information collection module is located directly below the nano-heterojunction scintillator detector and is used to collect scintillation information of different wavelengths emitted by each phase scintillator.

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