Zero-dimensional zinc-based halide scintillator material and preparation method and application thereof

Abstract

The invention relates to a zero-dimensional zinc-based halide scintillator material and a preparation method and application thereof, the chemical general formula of the zero-dimensional zinc-based halide scintillator material is (DPO) 2ZnX2, and X is Cl and / or Br. Through precise molecular design, in the obtained zero-dimensional zinc-based halide scintillator material, a central Zn < 2 + > ion, two halide ions and two nitrogen atoms from different DPO ligands are subjected to directional coordination, and a unique [ZnN2X2] < 2-> tetrahedral structure is formed. The tetrahedron serves as a built-in radiation sensitization unit and is tightly coupled with a DPO ligand serving as a light-emitting center on the molecular scale through strong chemical bonds (coordination bonds and ionic bonds), a zero-dimensional hybrid structure is jointly formed, efficient and rapid transfer of X-ray energy from a metal halide unit to an organic light-emitting center (DPO) is ensured, and the X-ray fluorescence intensity is improved. And the material has excellent thermal stability and excellent anti-radiation hardness, and is suitable for long-term and high-dose detection application.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to a zero-dimensional zinc-based halide scintillator material, its preparation method, and its uses. Background Technology

[0002] Scintillator materials are core components in fields such as X-ray imaging and security detection, capable of converting high-energy rays into visible light. Currently, the mainstream high-performance scintillators are inorganic crystals such as thallium-doped cesium iodide (CsI:Tl). Although they have high X-ray absorption efficiency and high light yield, their synthesis requires a high-temperature process, resulting in high costs, and their luminescence decay lifetime is relatively long (typically on the order of microseconds to milliseconds), which cannot meet the requirements of high-speed imaging.

[0003] In comparison, organic scintillators (such as anthracene and plastic scintillators) have attracted widespread attention due to their advantages such as rapid decay (nanosecond level), ease of processing, and low cost. However, due to the low atomic number (Z) of their constituent elements, they have weak X-ray absorption capabilities and generally low light yield, which limits their application in low-dose, high-sensitivity detection.

[0004] To balance high absorption and rapid decay, the following strategies can be adopted. For example, high-Z nanoparticles can be physically blended with organic dyes, but problems such as low energy transfer efficiency and susceptibility to concentration quenching still exist. Another approach is to utilize zero-dimensional organometallic halides, which have well-defined structures and are easy to synthesize. However, current research on this system mainly focuses on the autoluminescence of metal halide units (such as Mn). 2+ Sb 3+ Its light emission originates from d-electron transitions, resulting in a relatively long decay lifetime (microseconds), failing to leverage the advantage of rapid decay of organic components.

[0005] Current technologies have failed to effectively resolve the contradiction between high X-ray absorption and rapid luminescence decay. The fundamental reason lies in the lack of precise design of material structures at the molecular level to achieve efficient and rapid energy transfer between sensitization and luminescence units.

[0006] Therefore, how to develop a novel material that simultaneously achieves efficient radiation sensitization and rapid fluorescence emission through precise molecular design has become a key issue that urgently needs to be addressed in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a zero-dimensional zinc-based halide scintillator material, its preparation method, and its applications. The zero-dimensional zinc-based halide scintillator material of the present invention has the general chemical formula (DPO)₂ZnX₂, and possesses a precisely designed [ZnN₂X₂]₂ structure. 2- Tetrahedral structure, Zn 2+ With two Br -It coordinates with two N atoms from 2,5-diphenyloxazole (hereinafter referred to as DPO) to form [ZnN2Br2]. 2- Tetrahedron. This tetrahedron is separated by DPO, forming a zero-dimensional structure with excellent thermal stability and excellent radiation hardness resistance, making it suitable for long-term, high-dose detection applications.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a zero-dimensional zinc-based halide scintillator material, wherein the general chemical formula of the zero-dimensional zinc-based halide scintillator material is (DPO)2ZnX2, wherein DPO is 2,5-diphenyloxazole and X is Cl and / or Br.

[0010] This invention utilizes an intramolecular sensitization mechanism, employing high-Z-value metal halide units as radiation sensitizers and organic cations as luminescent centers, to achieve efficient energy transfer and rapid scintillation. It overcomes the shortcomings of existing organic and inorganic scintillators in terms of light yield, decay lifetime, and stability, providing a novel class of zero-dimensional zinc-based halide hybrid scintillator materials.

[0011] The zero-dimensional organometal halide hybrid single-crystal material provided by this invention is based on precise molecular-level design: central Zn 2+ Ions and two halide ions (X) - ) and two from different DPOs + The nitrogen atoms of the ligands undergo directional coordination to form a unique [ZnN2X2] structure. 2- Tetrahedral structure. The [ZnN2X2] tetrahedral structural unit is DPO. + The cations are spatially isolated to form a zero-dimensional hybrid structure. This tetrahedron, as a built-in radiation-sensitizing unit, is tightly coupled at the molecular scale with the DPO ligand, which is the luminescence center, through strong chemical bonds (coordination bonds and ionic bonds), together forming a zero-dimensional hybrid structure, thereby achieving efficient "molecular sensitization".

[0012] The zero-dimensional zinc-based halide scintillator material provided by this invention has the following advantages:

[0013] (1) Efficient intramolecular sensitization mechanism based on precise molecular-level design: This invention is not a simple physical mixing, but rather, through precise molecular design, it realizes for the first time the sensitization of Zn in the (DPO)2ZnX2 system. 2+ The directional coordination with nitrogen atoms in the organic ligands constructs a unique [ZnN2X2] molecule. 2-Tetrahedral structure. This close contact achieved at the molecular level through chemical bonds ensures efficient and rapid transfer of X-ray energy from metal halide units to organic light-emitting centers (DPO), fundamentally solving the dual problems of weak X-ray absorption in traditional organic scintillators and low energy transfer efficiency in physically blended systems.

[0014] (2) Balance between high light yield and rapid decay: The final light emission originates from the charge transition within the ligand of DPO, and the light yield is significantly higher than that of the traditional inorganic scintillator BGO (Bi4Ge3O). 12 ).

[0015] (3) Excellent stability: The material has a high thermal decomposition temperature (>260℃) and maintains stable structure and luminescence properties in air and high humidity environments for a long time.

[0016] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0017] Preferably, the space group of the zero-dimensional zinc-based halide scintillator material is P21 / n.

[0018] In a second aspect, the present invention provides a method for preparing a zero-dimensional zinc-based halide scintillator material as described in the first aspect, the method comprising the following steps:

[0019] The zero-dimensional zinc-based halide scintillator material is obtained by mixing 2,5-diphenyloxazole, zinc halide, and solvent and then reacting them under heating.

[0020] This invention utilizes a solution method (such as cooling a hot saturated solution crystallization method) to obtain single crystals with high crystallinity. This preparation method is green, low-cost, and easy to process; the synthesis process is simple, and it uses non-toxic, abundant zinc, meeting environmental protection requirements. The prepared material can be made into single crystals or composited with polymers to form flexible thin films, offering flexible applications.

[0021] Preferably, the molar ratio of 2,5-diphenyloxazole to zinc halide is 1.5-2.5:1, for example, it can be 1.5:1, 1.8:1, 2.0:1, 2.2:1 or 2.5:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] The molar ratio of 2,5-diphenyloxazole (DPO) to zinc halide (ZnX2) is a key factor in obtaining high-quality (DPO)2ZnX2 single crystals. This invention further controls the molar ratio of 2,5-diphenyloxazole to zinc halide to be from 1.5:1 to 2.5:1, more preferably 2:1. If the amount of DPO added is too large (e.g., >2.5:1), the excess organic cations will interfere with the normal crystallization process of the [ZnN2X2] tetrahedron, leading to the doping of uncoordinated DPO impurities in the crystal, or the formation of other impurity phases, thereby reducing the phase purity and scintillation performance of the material. If the amount of DPO added is too small (e.g., <1.5:1), it is impossible to obtain high-quality (DPO)2ZnX2 single crystals. 2+ Providing sufficient nitrogen atom coordination may lead to partial Zn 2+ It can coordinate only with halide ions to form unexpected low-dimensional structures (such as one-dimensional chain-like byproducts) or lead to incomplete crystal crystallization, which seriously affects the formation and stability of intramolecular sensitized structures.

[0023] Preferably, the zinc halide includes zinc chloride and / or zinc bromide.

[0024] Preferably, the solvent includes any one or a combination of at least two of acetonitrile, methanol, ethanol or DMF, with acetonitrile being the most preferred.

[0025] The inventors also discovered during their experiments that the reaction system must be kept in a non-acidic environment during the synthesis of (DPO)₂ZnX₂ single crystals, and the introduction of inorganic or organic acids is strictly prohibited. This is because the nitrogen atom in 2,5-diphenyloxazole (DPO) is the coordinating active center. Under acidic conditions, the nitrogen atom in DPO will preferentially protonate to form DPO-H⁺, and its coordination ability will decrease sharply, making it unable to react with Zn. 2+ The formation of stable Zn-N coordination bonds fundamentally disrupts the formation of the [ZnN2X2] tetrahedral structure, leading to synthesis failure.

[0026] Preferably, the mass ratio of zinc halide to solvent is 1:1-16, for example, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 or 1:16, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] This invention further controls the mass ratio of zinc halide to solvent to be 1:1-16. The mass ratio of zinc halide (ZnX2) to solvent is a key parameter for regulating crystal growth kinetics and obtaining ideal sizes and high-quality single crystals. If the amount of solvent is too large (i.e., the mass ratio is too small), the supersaturation of the reaction system is too low, resulting in insufficient nucleation driving force and extremely slow crystal growth, making it difficult to precipitate within a reasonable time, or only yielding microcrystals or powder. If the amount of solvent is too small (i.e., the mass ratio is too large), the system concentration is too high, and the supersaturation increases sharply, easily leading to instantaneous explosive nucleation and the generation of a large number of crystal nuclei. The result is often small, randomly stacked polycrystalline or flocculent precipitates, unable to grow large-size, high-integrity single crystals suitable for device fabrication.

[0028] In this invention, the mass ratio of zinc halide to solvent varies depending on the type of solvent. When acetonitrile is used as the solvent, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:8-16. Furthermore, when the zinc halide is ZnBr2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:12-16. When the zinc halide is ZnCl2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:8-12.

[0029] When N,N-dimethylformamide (DMF) is used as a solvent, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:4-9. Furthermore, when the zinc halide is ZnBr2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:6-9. When the zinc halide is ZnCl2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:4-6.

[0030] When methanol (MeOH) and / or ethanol (EtOH) are used as solvents, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:3-8. Furthermore, when the zinc halide is ZnBr2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:4-8. When the zinc halide is ZnCl2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:3-6.

[0031] Preferably, the heating reaction includes a heat preservation stage and a cooling stage.

[0032] Preferably, the insulation temperature during the insulation stage is 40℃-100℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] When preparing the precursor solution of (DPO)2ZnX2 single crystal, the temperature during the dissolution and clarification stages is crucial to ensuring complete dissolution of the raw material and obtaining a homogeneous and transparent solution.

[0034] The present invention further controls the preferred temperature range to be 40°C to 100°C, more preferably 60°C to 80°C. If the temperature is too high (e.g., >100°C), the solvent (e.g., acetonitrile and methanol) may evaporate too quickly, changing the solution concentration and composition. Simultaneously, excessive thermal stress may cause the decomposition or side reactions of the organic ligand (DPO), affecting the purity and performance of the final product. If the temperature is too low (e.g., <40°C), the dissolution kinetics are insufficient, and zinc halide and DPO may not dissolve completely, resulting in undissolved solid particles or microcrystals in the solution. These impurities can become heterogeneous nucleation centers, inducing the growth of impurity phases during subsequent crystallization, leading to impure products or severely damaging the integrity of the single crystal.

[0035] Preferably, the heat preservation time during the heat preservation stage is 6h-24h, for example, it can be 6h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] The heat preservation time of this invention is determined by whether the raw materials are completely dissolved. It is required that the raw materials are completely dissolved and a uniform and transparent solution is obtained within the heat preservation time.

[0037] Preferably, the cooling rate during the cooling stage is 1℃ / h-5℃ / h, for example, it can be 1℃ / h, 2℃ / h, 3℃ / h, 4℃ / h or 5℃ / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] The single crystal growth method of this invention adopts a cooling crystallization method. Its core lies in controlling the cooling rate to precisely regulate the supersaturation path of the solution, thereby dominating the nucleation and growth process of crystallization.

[0039] This invention further controls the cooling rate to 1°C / h to 5°C / h. Excessive high-speed cooling (>5°C / h) can lead to crystal defect proliferation and stress accumulation. For scintillator materials, these microscopic defects act as quenching centers, non-radiatively dissipating excited-state energy, directly resulting in a decrease in absolute light yield and deterioration of energy resolution. Simultaneously, the light scattering loss of the microcrystalline aggregates is severe, affecting light extraction efficiency. If ultra-low-speed cooling (<1°C / h) is used, for the zero-dimensional hybrid material of this invention, excessively slow growth may actually allow organic cations to undergo slow conformational rearrangement, introducing imperceptible long-range disorder, potentially affecting luminescence uniformity.

[0040] Therefore, a cooling rate of 1℃ / h–5℃ / h is an optimized kinetic window. It ensures that the solution slowly and steadily releases supersaturation within the metastable region, achieving a controllable, growth-driven process. This results in the preparation of single crystals with fewer defects, larger size, and higher optical uniformity, which is the material basis for obtaining high-yield, high-stability scintillators.

[0041] Preferably, after the heating reaction and before obtaining the zero-dimensional zinc-based halide scintillator material, the reaction product is further washed and dried.

[0042] Preferably, the solvent used for washing includes diethyl ether.

[0043] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0044] 2,5-Diphenyloxazole and zinc halide were dissolved in acetonitrile at a molar ratio of 1.5-2.5:1, with a mass ratio of zinc halide to acetonitrile of 1:8-16. The mixed solution was kept at 40℃-100℃ for 6h-24h, and then cooled to room temperature at a cooling rate of 1℃ / h-5℃ / h. The obtained product was washed with diethyl ether and then dried to obtain the zero-dimensional zinc-based halide scintillator material.

[0045] Thirdly, the present invention provides a use of the zero-dimensional zinc-based halide scintillator material as described in the first aspect, said zero-dimensional zinc-based halide scintillator material for the field of X-ray imaging.

[0046] The zero-dimensional zinc-based halide scintillator material provided by this invention has excellent optical and radiation resistance properties. Its X-ray excitation peak is located between 360-600 nm, which is beneficial for matching with detectors and reducing the response deviation of detectors caused by wavelength dependence of detection efficiency. Furthermore, under high-intensity irradiation of 17.4 mGy / s, the scintillation intensity remains stable, demonstrating excellent radiation resistance.

[0047] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The zero-dimensional organometal halide hybrid single crystal material provided by this invention is based on precise molecular-level design: central Zn 2+ The ion undergoes directional coordination with two halide ions and two nitrogen atoms from different DPO ligands to form a unique [ZnN2X2] ion. 2-Tetrahedral structure. This tetrahedron, as the built-in radiation-sensitizing unit, is tightly coupled at the molecular scale with the DPO ligand, which serves as the luminescence center, through strong chemical bonds (coordination bonds and ionic bonds), together forming a zero-dimensional hybrid structure, thereby achieving highly efficient "molecular sensitization".

[0050] (2) This invention prepares single crystals with high crystallinity through a solution method (such as cooling a hot saturated solution crystallization method). This preparation method is green, low-cost, and easy to process. The synthesis process is simple, and it uses non-toxic and abundant zinc, which meets environmental protection requirements. The prepared material can be made into single crystals or combined with polymers to form flexible films, allowing for flexible applications.

[0051] (3) The zero-dimensional zinc-based halide scintillator material provided by the present invention has excellent optical and radiation resistance properties. Its X-ray excitation peak is located between 360-600nm, which is beneficial for matching with the detector and reducing the response deviation of the detector due to the wavelength dependence of the detection efficiency. Furthermore, under high-intensity irradiation of 17.4mGy / s, the scintillation intensity remains stable, demonstrating excellent radiation resistance. Attached Figure Description

[0052] Figure 1 This is a single crystal structure diagram of (DPO)2ZnBr2 provided in Embodiment 1 of the present invention;

[0053] Figure 2 This is a single crystal structure diagram of (DPO)2ZnCl2 provided in Embodiment 2 of the present invention;

[0054] Figure 3 This is the powder X-ray diffraction pattern of (DPO)2ZnBr2 provided in Example 1 of this invention;

[0055] Figure 4 This is the powder X-ray diffraction pattern of (DPO)2ZnCl2 provided in Example 2 of the present invention;

[0056] Figure 5 This is the infrared spectrum of (DPO)2ZnBr2 provided in Embodiment 1 of the present invention;

[0057] Figure 6 These are the Raman spectra of (DPO)2ZnBr2, (DPO)2ZnCl2, and DPO provided in Embodiments 1, 2, and Comparative Example 1 of the present invention, respectively;

[0058] Figure 7 The thermogravimetric analysis curve of (DPO)2ZnBr2 provided in Embodiment 1 of the present invention;

[0059] Figure 8 The thermogravimetric analysis curve of (DPO)2ZnCl2 provided in Embodiment 2 of the present invention;

[0060] Figure 9 The image provided in Example 1 of this invention is a scanning electron microscope image of (DPO)2ZnBr2 and the corresponding elemental distribution diagrams of carbon, nitrogen, bromine, chlorine and zinc.

[0061] Figure 10 The image provided in Example 2 of this invention is a scanning electron microscope image of (DPO)2ZnCl2 and the corresponding elemental distribution diagrams of carbon, nitrogen, bromine, chlorine and zinc.

[0062] Figure 11 The UV-Vis absorption spectrum and Tauc curve of (DPO)2ZnBr2 provided in Example 1 of this invention are shown below.

[0063] Figure 12 The UV-Vis absorption spectrum and Tauc curve of (DPO)2ZnCl2 provided in Example 2 of this invention are shown below.

[0064] Figure 13 This is the photoluminescence spectrum (excitation and emission) of (DPO)2ZnBr2 provided in Embodiment 1 of the present invention and its luminescence photograph under ultraviolet light;

[0065] Figure 14 This is the photoluminescence spectrum (excitation and emission) of (DPO)2ZnCl2 provided in Embodiment 2 of the present invention and its luminescence photograph under ultraviolet light;

[0066] Figure 15 This is the CIE 1931 chromaticity coordinate diagram of (DPO)2ZnBr2 provided in Embodiment 1 of the present invention;

[0067] Figure 16 This is the CIE 1931 chromaticity coordinate diagram of (DPO)2ZnCl2 provided in Embodiment 2 of the present invention;

[0068] Figure 17 This is the temperature-varying emission spectrum of (DPO)2ZnBr2 at different temperatures provided in Embodiment 1 of the present invention;

[0069] Figure 18 This is the temperature-varying emission spectrum of (DPO)2ZnCl2 at different temperatures provided in Embodiment 2 of the present invention;

[0070] Figure 19 These are the radiation spectra of (DPO)2ZnBr2 and (DPO)2ZnCl2 under X-ray excitation provided in Embodiments 1, 2 and Comparative Example 1 of the present invention;

[0071] Figure 20 These are comparison diagrams showing the stability of (DPO)2ZnBr2, (DPO)2ZnCl2, and DPO under continuous high-intensity X-ray irradiation provided in Embodiments 1, 2, and Comparative Example 1 of the present invention.

[0072] Figure 21 The photoluminescence quantum yield of (DPO)2ZnBr2 provided in Embodiment 1 of this invention;

[0073] Figure 22 The photoluminescence quantum yield of (DPO)2ZnCl2 provided in Embodiment 2 of the present invention is shown. Detailed Implementation

[0074] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0075] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0076] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0077] Example 1

[0078] This embodiment provides a zero-dimensional zinc-based halide scintillator material, the chemical formula of which is (DPO)2ZnBr2;

[0079] The preparation method of the zero-dimensional zinc-based halide scintillator material provided in this embodiment includes the following steps:

[0080] 2,5-Diphenyloxazole and zinc bromide were dissolved in acetonitrile at a molar ratio of 2:1, and the mass ratio of zinc bromide to acetonitrile was 1:12. The mixed solution was kept at 60°C for 20 h, and then cooled to room temperature at a cooling rate of 2°C / h. The obtained product was washed with diethyl ether and then dried to obtain the zero-dimensional zinc-based halide scintillator material (DPO)2ZnBr2.

[0081] Example 2

[0082] This embodiment provides a zero-dimensional zinc-based halide scintillator material, the chemical formula of which is (DPO)₂ZnCl₂;

[0083] The preparation method of the zero-dimensional zinc-based halide scintillator material provided in this embodiment includes the following steps:

[0084] 2,5-Diphenyloxazole and zinc chloride were dissolved in DMF at a molar ratio of 2:1 and a mass ratio of zinc chloride to DMF of 1:6. The mixed solution was kept at 70°C for 15 h, and then cooled to room temperature at a cooling rate of 1°C / h. The obtained product was washed with diethyl ether and then dried to obtain the zero-dimensional zinc-based halide scintillator material (DPO)2ZnCl2.

[0085] Example 3

[0086] This embodiment provides a zero-dimensional zinc-based halide scintillator material, the chemical formula of which is (DPO)2ZnBr2;

[0087] The preparation method of the zero-dimensional zinc-based halide scintillator material provided in this embodiment includes the following steps:

[0088] 2,5-Diphenyloxazole and zinc bromide were dissolved in methanol at a molar ratio of 2.5:1 and a mass ratio of zinc bromide to methanol of 1:4. The mixed solution was kept at 80°C for 12 h, and then cooled to room temperature at a cooling rate of 5°C / h. The obtained product was washed with diethyl ether and then dried to obtain the zero-dimensional zinc-based halide scintillator material (DPO)2ZnBr2.

[0089] Example 4

[0090] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Example 1 is that, in preparing this zero-dimensional zinc-based halide scintillator material, 2,5-diphenyloxazole and zinc bromide are prepared in a molar ratio of 1:1, while the other steps remain unchanged.

[0091] Example 5

[0092] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Example 1 is that, in preparing this zero-dimensional zinc-based halide scintillator material, 2,5-diphenyloxazole and zinc bromide are prepared in a molar ratio of 3:1, while the other steps remain unchanged.

[0093] Example 6

[0094] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Embodiment 1 is that the mass ratio of zinc bromide to acetonitrile is 1:20 when preparing the zero-dimensional zinc-based halide scintillator material, while the other steps remain unchanged.

[0095] Example 7

[0096] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Embodiment 1 is that the mass ratio of zinc bromide to acetonitrile is 1:4 when preparing the zero-dimensional zinc-based halide scintillator material, while the other steps remain unchanged.

[0097] Example 8

[0098] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Embodiment 1 is that the heat preservation temperature is changed from 60°C to 30°C when preparing the zero-dimensional zinc-based halide scintillator material, while the other steps remain unchanged.

[0099] Example 9

[0100] This embodiment provides a zero-dimensional zinc-based halide scintillator material. The only difference from Embodiment 1 is that the heat preservation temperature is changed from 60°C to 120°C when preparing the zero-dimensional zinc-based halide scintillator material, while the other steps remain unchanged.

[0101] Comparative Example 1

[0102] This comparative example provides a DPO material, which differs from Example 1 only in that zinc bromide was not added during the preparation of this DPO material.

[0103] Comparative Example 2

[0104] This comparative example provides a scintillator material, which differs from Example 1 only in that, in preparing this scintillator material, 2,5-diphenyloxazole and zinc bromide are dissolved in a mixed solution of acetonitrile and HBr at a molar ratio of 2:1, and the volume ratio of acetonitrile to HBr is 2:1.

[0105] Comparative Example 3

[0106] This comparative example provides a scintillator material, which differs from Example 1 only in that, in preparing this scintillator material, 2,5-diphenyloxazole is replaced with an equimolar amount of tetraphenylphosphine bromide (TPP). + Br - ).

[0107] test:

[0108] (1) Single crystal structure: X-ray single crystal diffraction data of zero-dimensional zinc-based halides in different space groups were collected by radiation from a copper target (λ=0.154187nm) on the Rigaku XtaLAB Synergy Custom X-ray single crystal diffractometer.

[0109] (2) X-ray photoelectron spectroscopy: The elemental composition and valence state were analyzed using an ESCALAB 250Xi X-ray photoelectron spectroscopy instrument from Thermo Fisher Scientific, USA.

[0110] (3) SEM and Mapping Analysis: The microstructure of the material was observed using a Hitachi SU8010 scanning electron microscope. In addition, the elemental micro-area semi-quantitative analysis and surface scan elemental distribution were performed using the equipped Energy Dispersive X-ray Spectroscopy (EDX).

[0111] (4) Thermal analysis: Thermogravimetric-differential thermal analysis (TGA-DSC) was performed using a NETZSCH STA449F3 integrated thermal analyzer. The test was conducted under an N2 gas atmosphere to obtain the TGA-DSC curves.

[0112] (5) Luminescence Performance Test: Photoluminescence: The luminescence spectrum of the material was monitored using an Edinburgh Instruments FLS1000 fluorescence spectrometer. The excitation source was a continuous xenon lamp (450W), and the detector was a photomultiplier tube (Hamamatsu R928). Scanning was performed with a scan step size of 0.5 nm and an integration time of 0.2 seconds per step. To ensure the reliability and accuracy of the test results, after the instrument was calibrated to the standard, filters of appropriate specifications were added during the test to remove interference from ambient light, excitation light, and instrument noise. All samples for intensity comparison were subjected to spectral testing under exactly the same conditions.

[0113] (6) Low-temperature spectroscopy: The in-situ temperature-varying spectra of the samples were tested using a Linkam Scientific Instruments THMS 600 powder stage and an FLS1000 spectrometer based on fiber optic signal transmission. The process relied on an external liquid nitrogen circulation system for cooling, and the testable temperature range was 77-800K. The specific spectroscopic test method was the same as described above.

[0114] (7) Radiation emission characterization: Radiation emission (RL) spectra were acquired using a self-built setup with an X-ray tube (12W, TUB00146-W06, Magpro) and a fiber optic spectrometer (PG2000Pro, Ideaoptics). The X-ray source was a tungsten target source with a maximum power of 12W, a maximum voltage of 70kV, a maximum current of 200μA, and an X-ray photon quantity of 69.5keV. The X-ray dose rate was calibrated using a high-sensitivity, wide-range X-ray radiation detector (ATOMTEXAT1121).

[0115] The zero-dimensional zinc-based halide scintillator materials prepared in the examples and comparative examples were tested, and the test results are shown in Table 1 below. Figures 1-20 As shown.

[0116] from Figure 1 and Figure 2 It can be seen that the zero-dimensional zinc-based halide scintillator materials obtained in Examples 1 and 2 are made from Zn 2+ A unique zero-dimensional [ZnN2Br2] is formed by coordination with halide ions and nitrogen atoms in the DPO ligand. 2- and [ZnN2Cl2] 2- The tetrahedral structural unit has a space group of P21 / n. The key structural feature is Zn. 2+ With two Br - It coordinates with two N atoms from DPO to form [ZnN2Br2]. 2- The tetrahedron is separated by DPO, forming a zero-dimensional structure.

[0117] from Figure 3 and Figure 4 It can be seen that the experimental spectra of the zero-dimensional zinc-based halide scintillator materials obtained in Examples 1 and 2 are in complete agreement with the spectra based on single-crystal structure simulation, confirming the high phase purity of the obtained materials.

[0118] from Figure 5 It can be seen that at 1500cm -1 The changes in the regional signal reflect the successful formation of Zn-N coordination bonds.

[0119] from Figure 6 It can be known that it is located at approximately 140-500cm. -1 A series of characteristic peaks further corroborate the formation of intramolecular Zn-N and Zn-X coordination bonds.

[0120] Among them, the Raman spectrum shows Zn-N bond vibrational signals in the low wavenumber region, while the intensity of the C=N bond characteristic peak decreases; the infrared spectrum is in the ~1600 cm⁻¹ region. -1 The appearance of a new peak is attributed to the vibrational changes after the coordination of C=N with Zn. Both of these factors jointly confirm the formation of the Zn-N coordination bond, providing evidence from the chemical bond level for the successful realization of the pre-set molecular structure, which is the structural prerequisite for molecular sensitization.

[0121] from Figure 7 and Figure 8 It can be seen that the zero-dimensional zinc-based halide scintillator materials obtained in Examples 1 and 2 do not have significant mass loss before 269°C, indicating that the zero-dimensional zinc-based halide scintillator materials provided by the present invention only begin to decompose at high temperatures (>260°C), proving that they have excellent thermal stability and can meet the temperature requirements of the device during operation.

[0122] from Figure 9 and Figure 10As can be seen, the zero-dimensional zinc-based halide scintillator materials obtained in Examples 1 and 2 show regular crystal morphology under SEM, and EDS surface scan analysis shows that C, N, Br, and Zn elements are uniformly distributed in the crystal, which proves the good crystallinity and compositional homogeneity of the material, and confirms the regularity of the crystal and the compositional homogeneity.

[0123] from Figure 11 and Figure 12 It can be seen that the zero-dimensional zinc-based halide scintillator materials obtained in Examples 1 and 2 are indirect bandgap semiconductors, with Eg values ​​of 3.14 eV and 2.98 eV, respectively. Under UV excitation, the (DPO)₂ZnBr₂ obtained in Example 1 exhibits a deep blue emission with a peak value of ~398 nm, and CIE chromaticity coordinates of (0.162, 0.035), showing good color purity.

[0124] from Figure 13 and 14 It is known that the zero-dimensional zinc-based halide scintillator material provided by the present invention produces strong deep blue light emission at about 398 nm.

[0125] from Figure 15 and 16 It can be seen that its coordinates are located in the deep blue light region, which proves the color purity of the light emitted by the zero-dimensional zinc-based halide scintillator material provided by the present invention.

[0126] from Figure 17 and Figure 18 As can be seen, the temperature-dependent emission spectrum shows a "reverse thermal quenching" phenomenon where the luminescence intensity first decreases and then increases with temperature. Furthermore, the evolution of the dual emission peaks with temperature is observed, indicating the existence of two distinct luminescent centers or excited-state processes within the material. This may be related to the sensitization-emission pathway and exciton localization. The zero-dimensional zinc-based halide scintillator material provided by this invention exhibits excellent fluorescence thermal stability.

[0127] from Figure 19 It can be seen that by comparing the X-ray excitation (RL) spectra of (DPO)₂ZnBr₂ and pure DPO raw materials, Figure 11 It can be observed that the RL intensity of the hybrid material is significantly enhanced, and the emission peak exhibits a redshift and a significantly broadened full width at half maximum (FWHM). This directly proves the existence of [ZnN2Br2]. 2- The tetrahedron, acting as a radiation sensitizer, efficiently absorbs X-ray energy and transfers it to the DPO luminescent center through intramolecular channels, thus achieving "molecular sensitization." This provides more direct kinetic evidence for the molecular sensitization mechanism. Compared with the pure organic DPO raw material in Comparative Example 1, the zero-dimensional zinc-based halide scintillator material provided by this invention exhibits a redshift of the emission peak and a significant broadening of the full width at half maximum (FWHM), directly demonstrating the molecular sensitization effect of the metal halide unit on the organic luminescent center.

[0128] from Figure 20 It can be seen that under continuous high-intensity X-ray irradiation of 17.4 mGy / s, the scintillation intensity of pure DPO molecules in Comparative Example 1 rapidly decays, while the intensity of (DPO)2ZnBr2 in Example 1 remains stable. The zero-dimensional zinc-based halide scintillator material provided by the present invention has excellent radiation resistance and is suitable for long-term, high-dose detection applications.

[0129] from Figure 21 and Figure 22 As can be seen, the photoluminescence quantum yield of Example 1 (DPO)₂ZnBr₂ is 23.98%, demonstrating its basic performance as a scintillator material. The photoluminescence quantum yield of Example 2 (DPO)₂ZnCl₂ reaches 53.68%, significantly higher than its bromide counterparts. This comparison directly proves that, within the structural framework described in this invention, replacing the halogen anion from Br⁻ to Cl⁻ is an effective technical means to improve the luminescence efficiency of the material, pointing the way for further optimization of material performance.

[0130] Table 1

[0131]

[0132] The test results show that:

[0133] (1) As can be seen from Examples 1-3, the present invention obtains a zero-dimensional zinc-based halide scintillator material with the general chemical formula (DPO)2ZnX2 through precise molecular design. The central Zn in this material 2+ The ion undergoes directional coordination with two halide ions and two nitrogen atoms from different DPO ligands to form a unique [ZnN2X2] ion. 2- Tetrahedral structure. This tetrahedron, acting as a built-in radiation-sensitizing unit, is tightly coupled at the molecular scale with the DPO ligand, which serves as the luminescent center, through strong chemical bonds (coordination and ionic bonds), forming a zero-dimensional hybrid structure, thus achieving highly efficient "molecular sensitization." This ensures efficient and rapid transfer of X-ray energy from the metal halide unit to the organic luminescent center (DPO), fundamentally solving the dual problems of weak X-ray absorption in traditional organic scintillators and low energy transfer efficiency in physically blended systems. Furthermore, the zero-dimensional zinc-based halide scintillator material obtained through the hot solvent method exhibits excellent thermal stability and excellent radiation hardness, making it suitable for long-term, high-dose detection applications.

[0134] (2) A comparison of Example 1 with Examples 4-5 shows that the present invention further controls the molar ratio of 2,5-diphenyloxazole and zinc halide to be 1.5:1 to 2.5:1, more preferably 2:1. If the amount of DPO added is too large (e.g., >2.5:1), the excessive organic cations will interfere with the normal crystallization process of [ZnN2X2] tetrahedra, resulting in the doping of uncoordinated DPO impurities in the crystal, or the generation of other impurity phases, thereby reducing the phase purity and scintillation performance of the material. If the amount of DPO added is too small (e.g., <1.5:1), it is not possible to provide all Zn 2+ Providing sufficient nitrogen atom coordination may lead to partial Zn 2+ It can coordinate only with halide ions to form unexpected low-dimensional structures (such as one-dimensional chain-like byproducts) or lead to incomplete crystal crystallization, which seriously affects the formation and stability of intramolecular sensitized structures.

[0135] (3) A comparison between Example 1 and Examples 6-7 shows that further controlling the mass ratio of zinc halide to solvent to be 1:1-16 is crucial. The mass ratio of zinc halide (ZnX2) to solvent is a key parameter for regulating crystal growth kinetics and obtaining ideal size and high-quality single crystals. If the amount of solvent is too large (i.e., the mass ratio is too small), the supersaturation of the reaction system will be too low, resulting in insufficient nucleation driving force and extremely slow crystal growth, making it difficult to precipitate within a reasonable time, or only microcrystals or powder will be obtained. If the amount of solvent is too small (i.e., the mass ratio is too large), the system concentration will be too high, and the supersaturation will increase sharply, easily leading to instantaneous explosive nucleation and generating a large number of crystal nuclei. The result is often obtaining small-sized, randomly stacked polycrystalline or flocculent precipitates, unable to grow large-sized, high-integrity single crystals suitable for device processing. In this invention, the mass ratio of zinc halide to solvent will vary depending on the type of solvent. When acetonitrile is used as a solvent, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:8-16. Furthermore, when the zinc halide is ZnBr2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:12-16. When the zinc halide is ZnCl2, the mass ratio of zinc halide (ZnX2) to acetonitrile is more preferably 1:8-12.

[0136] (4) By comparing Example 1 with Examples 8-9, it can be seen that the present invention further controls the preferred temperature range of 40°C to 100°C. If the temperature is too high (e.g., >100°C), the solvent may evaporate too quickly (e.g., acetonitrile and methanol), changing the solution concentration and composition. At the same time, excessive thermal stress may cause the decomposition or side reactions of organic ligands (DPO), affecting the purity and performance of the final product. If the temperature is too low (e.g., <40°C), the dissolution kinetics are insufficient, and zinc halide and DPO may not be completely dissolved, resulting in undissolved solid particles or microcrystals in the solution. These impurities will become heterogeneous nucleation centers, inducing the growth of impurity phases during subsequent crystallization, leading to impure products or severely damaging the integrity of single crystals.

[0137] (5) As can be seen from Example 1 and Comparative Example 1, the (DPO)2ZnBr2 material prepared in Example 1 of this invention, with its [ZnN2Br2] tetrahedron as a built-in highly efficient radiation sensitizer, ensures the efficient transfer of excitation energy from the inorganic unit to the organic luminescent center, thereby achieving a doubling of X-ray excitation emission (RL) signal and maintaining stability under irradiation. However, when the intramolecular sensitization design of this invention is not adopted (i.e., the metal halide sensitizing unit is lacking), as shown in Comparative Example 1, the pure organic DPO material cannot form an effective energy transfer channel. Therefore, it cannot achieve the same level of X-ray absorption efficiency and scintillation performance, specifically manifested as a significant reduction in X-ray excitation emission (RL) intensity, far lower than that of the material of this invention, fully demonstrating the indispensable key role of the metal halide unit as a molecular sensitizer in this invention.

[0138] In summary, this invention, through precise molecular design, yields a zero-dimensional zinc-based halide scintillator material with the general chemical formula (DPO)₂ZnX₂, in which the central Zn... 2+ The ion undergoes directional coordination with two halide ions and two nitrogen atoms from different DPO ligands to form a unique [ZnN2X2] ion. 2- Tetrahedral structure. This tetrahedron, acting as a built-in radiation-sensitizing unit, is tightly coupled at the molecular scale with the DPO ligand, which serves as the luminescent center, through strong chemical bonds (coordination and ionic bonds), forming a zero-dimensional hybrid structure, thus achieving highly efficient "molecular sensitization." This ensures efficient and rapid transfer of X-ray energy from the metal halide unit to the organic luminescent center (DPO), fundamentally solving the dual problems of weak X-ray absorption in traditional organic scintillators and low energy transfer efficiency in physically blended systems. Furthermore, the zero-dimensional zinc-based halide scintillator material obtained through the hot solvent method exhibits excellent thermal stability and excellent radiation hardness, making it suitable for long-term, high-dose detection applications.

[0139] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A zero-dimensional zinc-based halide scintillator material, characterized in that, The chemical formula of the zero-dimensional zinc-based halide scintillator material is (DPO)2ZnX2, where DPO is 2,5-diphenyloxazole and X is Cl and / or Br.

2. The zero-dimensional zinc-based halide scintillator material according to claim 1, characterized in that, The space group of the zero-dimensional zinc-based halide scintillator material is P21 / n.

3. A method for preparing a zero-dimensional zinc-based halide scintillator material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: The zero-dimensional zinc-based halide scintillator material is obtained by mixing 2,5-diphenyloxazole, zinc halide, and solvent and then reacting them under heating.

4. The preparation method according to claim 3, characterized in that, The molar ratio of 2,5-diphenyloxazole to zinc halide is 1.5-2.5:1; Preferably, the zinc halide includes zinc chloride and / or zinc bromide.

5. The preparation method according to claim 3 or 4, characterized in that, The solvent includes any one or a combination of at least two of acetonitrile, methanol, ethanol or DMF, preferably acetonitrile; Preferably, the mass ratio of zinc halide to solvent is 1:1-16.

6. The preparation method according to claim 5, characterized in that, The heating reaction includes a heat preservation stage and a cooling stage; Preferably, the insulation temperature during the insulation stage is 40℃-100℃; Preferably, the heat preservation time during the heat preservation stage is 6h-24h.

7. The preparation method according to claim 5 or 6, characterized in that, The cooling rate during the cooling phase is 1℃ / h - 5℃ / h.

8. The preparation method according to any one of claims 3-7, characterized in that, Before obtaining the zero-dimensional zinc-based halide scintillator material after the heating reaction, the reaction product is also washed and dried. Preferably, the solvent used for washing includes diethyl ether.

9. The preparation method according to any one of claims 3-8, characterized in that, The preparation method includes the following steps: 2,5-Diphenyloxazole and zinc halide were dissolved in acetonitrile at a molar ratio of 1.5-2.5:1, with a mass ratio of zinc halide to acetonitrile of 1:8-16. The mixed solution was kept at 40℃-100℃ for 12h-24h, and then cooled to room temperature at a cooling rate of 1℃ / h-5℃ / h. The obtained product was washed with diethyl ether and then dried to obtain the zero-dimensional zinc-based halide scintillator material.

10. The use of a zero-dimensional zinc-based halide scintillator material as described in claim 1 or 2, characterized in that, The zero-dimensional zinc-based halide scintillator material is used in the field of X-ray imaging.

Images