Polymeric phosphor scintillators responsive to x-rays and methods of making and using the same

Abstract

The application discloses an X-ray responsive polymer phosphorescent scintillator and a preparation method and application thereof; specifically, a halogenated monomer and an acrylic acid monomer are subjected to free radical copolymerization, the feeding ratio of the monomers is changed, copolymers with different halogenated monomer contents are synthesized, and the influence of these factors and the introduction of halogen atoms on the absorption of X-rays and the radiation luminescence performance is investigated; meanwhile, by changing the structure of the halogenated monomer, we realize colorful phosphorescent emission under X-ray excitation, which proves the universality of the design principle; in addition, the copolymers exhibit good processability, film-forming property and X-ray responsiveness, and have good application prospects in the fields of flexible X-ray imaging and large-area display.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials technology, specifically relating to an X-ray responsive polymer phosphorescent scintillator technology. Background Technology

[0002] In recent years, with the continuous development of life sciences and military defense, the development of scintillator materials has gradually attracted widespread attention. Among them, X-ray scintillators are a class of luminescent materials with X-ray response. These materials have the special ability to convert high-energy X-ray photons into low-energy visible or ultraviolet light, and have played a significant role in radiation detection, security inspection, military defense, biomedicine (such as bioimaging and radiotherapy), and high-energy ray astronomical observation.

[0003] Currently, high-performance X-ray scintillators are mostly inorganic crystals or metal-organic complexes. They contain heavy metal elements with high atomic numbers (z), exhibiting excellent scintillation properties such as strong X-ray blocking ability, high light output, and low detection limit. However, in practical preparation and application, these materials still face key limitations such as stringent preparation conditions, difficulty in assembly, and high cost.

[0004] In response to the demands of energy conservation and environmental protection in economic development, organic scintillators, especially plastic scintillators, have gained increasing favor among researchers in recent years due to their advantages such as inexpensive raw materials, ease of modification, and preparation, becoming a powerful alternative to traditional inorganic scintillators. Generally, plastic scintillators are mainly composed of low atomic number organic conjugated chromophores, resulting in weak X-ray absorption and radiative emission. Therefore, to improve the performance of traditional plastic scintillators, it is necessary to embed organometallic complexes or nanoparticles containing heavy metals and fluorescent dyes into polymer systems through complex preparation processes, which inevitably hinders their practical application. Furthermore, most organic scintillators are fluorescent molecules, meaning that only 25% of singlet excitons can be collected and used for emission, while approximately 75% of triplet excitons are dissipated through non-radiative decay and are not effectively utilized. This may be another factor contributing to the weak light output of organic scintillators.

[0005] In contrast, phosphorescence emission from purely organic materials originates from radiative transitions of triplet excitons. In this case, 75% of triplet excitons can be effectively utilized. Furthermore, phosphorescent materials possess excellent photophysical properties, such as environmentally sensitive emission wavelengths, large Stokes shifts, and long emission lifetimes. Therefore, the development of organic phosphorescent scintillators is of great significance for technological innovation. The introduction of heavy halogen atoms not only increases spin-orbit coupling in purely organic materials, thereby promoting intersystem crossing processes and achieving efficient room-temperature phosphorescence emission, but also enhances the X-ray absorption capacity of metal-free luminescent materials, promoting radiative luminescence. Therefore, the development of purely organic phosphorescent scintillators has achieved a technological breakthrough and shows promising application prospects in X-ray imaging, non-destructive testing, and other fields. Summary of the Invention

[0006] The purpose of this invention is to provide an X-ray responsive polymer phosphorescent scintillator, its preparation method, and its application. By utilizing the good reproducibility, processability, film-forming properties, and flexibility of polymers, the inherent obstacles of organic crystal materials in device integration and processing performance are overcome. A low-cost, easy-to-implement, large-area fabrication polymer phosphorescent scintillator with X-ray responsive performance is developed to solve one of the problems mentioned in the background art.

[0007] To achieve the above objectives, in one aspect, the present invention provides a polymer phosphorescent scintillator with X-ray response, the general structural formula of which is as follows:

[0008]

[0009] In the general formula, n+m=1, and m is 0-0.5.

[0010] In another aspect, the present invention also provides a method for preparing a polymer phosphorescent scintillator with X-ray response, comprising the following steps:

[0011] (1) Synthesis of halogenated monomers;

[0012] (2) The target polymer material is prepared by free radical copolymerization of the halogenated monomers in step (1) and acrylic acid; wherein the reaction conditions for free radical polymerization are AIBN / toluene / nitrogen environment / heating and reflux.

[0013] The characteristic of this type of polymer lies in the fact that the introduction of halogen atoms can effectively promote intersystem crossing processes and the material's absorption capacity for X-rays, thereby producing phosphorescent scintillation characteristics. Furthermore, under different doses of X-ray excitation, the radiative emission intensity of this type of polymer scintillator exhibits linear response characteristics. Since the content of halogenated monomers affects the material's X-ray absorption and luminescence efficiency, the radiative emission intensity of this type of scintillator is significantly dependent on the monomer feed ratio. In addition, by modifying the structure of the halogenated monomers, multicolored phosphorescent emission under X-ray excitation can be achieved.

[0014] Because of their excellent processability, film-forming properties, and X-ray responsiveness, these polymer materials can be used in fields such as flexible X-ray imaging and large-area displays.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The structures of halogenated monomers and polymer materials were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS). The thermal stability of the materials was characterized by thermogravimetric analysis (TGA) and differential thermal analysis (DSC). The photophysical properties of this series of polymer films were studied in detail by measuring ultraviolet absorption spectroscopy, photofluorescence / phosphorescence spectroscopy, fluorescence / phosphorescence lifetime, quantum efficiency, and radiative emission spectroscopy, exploring the relationship between polymer structure and luminescence performance. The influencing factors of polymer radiative emission were studied by changing the polymerization ratio of halogenated monomers. The packing form of polymer structural units was characterized by X-ray diffraction (XRD) and wide-angle scattering (WAXS). The molecular orbital transition components, energy level changes, and electron cloud distribution of polymer repeating units were calculated and simulated using Gaussian 09 software to explore the luminescence mechanism of X-ray scintillator radiative emission.

[0017] The excellent processability, film-forming properties, flexibility, and X-ray responsiveness of this type of polymer material enable its application in X-ray imaging, non-destructive testing, and flexible displays. Attached Figure Description

[0018] Figure 1 The images show the steady-state photoluminescence, phosphorescence, and radiative emission spectra of the polymer films synthesized in this invention at room temperature.

[0019] Figure 2 The images show the radiative emission spectra of polymer films with different halogenated monomer contents synthesized in this invention under the same conditions.

[0020] Figure 3 The graph shows the variation of radiative emission intensity and linear response of the polymer film synthesized in this invention under X-ray excitation at different dose rates.

[0021] Figure 4 The graph shows the variation of the radiative emission intensity of the polymer film synthesized in this invention under continuous excitation by high dose rate X-rays (278.0 μGy s⁻¹).

[0022] Figure 5 This is a radiation emission spectrum of polymer films with different halogenated monomer structures synthesized in this invention under the same conditions. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] Preparation of halogenated monomer materials:

[0026] Preparation of compound 1: 1,4-diallyloxy-2,5-diiodobenzene;

[0027] 1 g of 1,4-dihydroxy-2,5-diiodobenzene (2.76 mmol), 0.84 g of 3-bromopropene (6.94 mmol), and 0.78 g of KOH (13.9 mmol) were added to a round-bottom flask, and 20 ml of DMF was poured in to dissolve them. The mixture was stirred at room temperature for 2 hours. After the reaction was complete, the KOH was filtered off, the filtrate was collected, and the solvent was removed by rotary evaporation. The resulting solid was extracted three times with saturated brine and dichloromethane, the organic layer was collected, sand was prepared, and the product was purified by column chromatography to obtain a white solid (0.78 g, 63.9%). 1 HNMR (500MHz, CDCl3) δ7.21-7.03(m,2H),6.19-5.94(m,2H),5.48(d,2H),5.33(d,2H),4.56(dd,4H). 13 C NMR (126MHz, CDCl3) δ149.79(s), 132.41(s), 118.91(s), 118.09(s), 111.24(s), 70.77(s).

[0028] Preparation of compound 2: 1-allyloxy-4-bromonaphthalene;

[0029] 1 g of 4-bromonaphthol (4.48 mmol), 0.65 g of 3-bromopropene (5.37 mmol), and 0.75 g of KOH (13.37 mmol) were added to a round-bottom flask and dissolved in 20 ml of DMF. The mixture was stirred at room temperature for 2 hours. After the reaction was complete, the KOH was filtered off, the filtrate was collected, and the solvent was removed by rotary evaporation. The resulting solid was extracted three times with saturated brine and dichloromethane. The organic layer was collected, sand was prepared, and the product was purified by column chromatography to obtain a white solid (0.95 g, 81.20%). 1 H NMR (500MHz, CDCl3) δ7.95(dd,1H),7.65(dd,1H),7.60(t,1H),7.56-7.44(m,1H),7.32-7.25(m,1 H),7.26-7.16(m,1H),6.21-6.09(m,1H),5.55-5.42(m,1H),5.42-5.29(m,1H),4.68(dt,2H).13C NMR(126MHz, CDCl3)δ156.84(s),132.99(d),130.09(s),129.65(d),128.5 5(s),128.42(s),120.04(s),117.98(s),117.14(s),107.01(s),68.89(s).

[0030] Preparation of compound 3: 2,2'-bis(allyloxy)-6,6'-dibromo-1,1'-binaphthalene;

[0031] 1 g of 6,6'-dibromo-1,1'-bi-2-naphthol (2.25 mmol), 0.68 g of 3-bromopropene (5.63 mmol), and 0.63 g of KOH (11.25 mmol) were added to a round-bottom flask and dissolved in 20 ml of DMF. The mixture was stirred at room temperature for 2 hours. After the reaction was complete, the KOH was filtered off, the filtrate was collected, and the solvent was removed by rotary evaporation. The resulting solid was extracted three times with saturated brine and dichloromethane. The organic layer was collected, sand was prepared, and the product was purified by column chromatography to obtain a white solid (0.76 g, 64.40%). 1 H NMR (500MHz, CDCl38.04(d,2H),7.86(d,2H),7.44(d,2H),7.30(dd,2H),7.02(d,2H),5.82-5.72(m,2H),5.09-4.99(m,4H),4.55(dt,4H). 13C NMR(126MHz, CDCl3)δ154.27(s),133.34(s),132.52(s),130.32(s),129.87(s),129.6 6(s),128.51(s),127.11(s),119.85(s),117.48(s),116.71(s),116.43(s),69.82(s).

[0032] Example 2: Preparation of a polymer (PNBr) film containing bromonaphthalene;

[0033] 0.2 g (0.76 mmol) of 1-allyloxy-4-bromonaphthalene monomer, 20 mg of azobisisobutyl, and 2.74 g (38.02 mmol) of acrylic acid were weighed and added to a single-necked round-bottom flask, which was then sealed with a rubber stopper. The reaction mixture was evacuated, purged with nitrogen, and evacuated again three times using a double-row tube system. Finally, nitrogen was used to protect the reaction system. Then, 40 mL of toluene obtained by dry distillation was added. The reaction mixture was refluxed and stirred at 75 °C for 18 hours, then cooled to room temperature and filtered to obtain a white solid. The solid was then washed several times with dichloromethane, and the washed white solid was dissolved in deionized water. Finally, the polymer aqueous solution was dialyzed in a dialysis bag (MWCO = 2000) for 72 hours. The dialyzed polymer aqueous solution was then introduced into a polytetrafluoroethylene mold and dried at 60 °C for 12 hours to obtain a polymer film. By changing the molar ratio of halogenated monomers to acrylic acid, a series of copolymers with different halogenated monomer contents can be obtained by following the above method.

[0034] Example 3: Experiment investigating X-ray response characteristics and photostability;

[0035] Polymer films with the strongest radioluminescence intensity were selected from copolymers with different halogenated monomer contents to investigate their X-ray response characteristics and photostability. When the X-ray dose rate increased from 0.69 μGy s⁻¹ to 278.0 μGy s⁻¹, the radioluminescence spectra of the polymer films were collected, and the collected data were plotted with dose rate on the x-axis and radioluminescence intensity on the y-axis. The test data showed that the intensity of polymer radioluminescence exhibited a good linear response with the change of X-ray dose rate. Furthermore, under continuous excitation by high-dose-rate X-rays (278.0 μGy s⁻¹), the intensity of polymer radioluminescence remained essentially unchanged, demonstrating excellent photostability.

[0036] Example 4: Experimental study on the scintillation properties of polymers with different halogenated monomer structures;

[0037] Monomers with conjugated structures such as halobenzene, halocarbazole, halonaphthalene, and halobinaphthol were selected and polymerized with acrylic acid monomers according to the above polymerization method to obtain polymer films containing different halomonomer structures. The above polymer films were subjected to radioluminescence spectroscopy tests, and it was found that under X-ray (278.0 μGy s-1) excitation, the emission peak of the radioluminescence spectrum gradually red-shifted, realizing colorful phosphorescence emission under X-ray excitation; this also confirms the universality of the strategy for constructing polymer phosphorescent scintillators proposed in this invention.

[0038] Example 5: An experimental study on the application of polymer phosphorescent scintillators;

[0039] Since polyacrylic acid is a water-soluble polymer, the above polymer is dissolved in deionized water and stirred evenly. The polymer aqueous solution is then poured into a polytetrafluoroethylene mold, heated and dried to form the final product, and then demolded. The resulting uniform and transparent polymer film is used as an imaging background, with seashells, metals, etc., used as imaging objects, an X-ray source as the excitation source, and a common commercial camera as the imaging capture device. Ultimately, this type of polymer phosphorescent scintillator can be applied in X-ray imaging, non-destructive testing, and flexible displays.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of making a polymer phosphor scintillator having an x-ray response, characterized by: The preparation method includes: (1) Synthesis of halogenated monomers, the synthesized halogenated monomers are 1-allyloxy-4-bromonaphthalene monomers; (2) The halogenated monomers from step (1) are copolymerized with acrylic acid to prepare the target polymer film via free radical copolymerization; The reaction conditions for free radical polymerization were AIBN / toluene / nitrogen atmosphere / heating and reflux; the molar ratio of 1-allyloxy-4-bromonaphthalene monomer to acrylic acid was 0.76:38.

02. After the free radical copolymerization was completed, a white solid was obtained. The solid was then washed multiple times with dichloromethane and dissolved in deionized water. Finally, the polymer aqueous solution was placed in a dialysis bag and dialyzed for 72 hours. The dialyzed polymer aqueous solution was then introduced into a polytetrafluoroethylene mold and dried at 60°C for 12 hours to obtain a uniform and transparent polymer film. The polymer film can serve as an imaging background, enabling the polymer phosphorescent scintillator to be used in X-ray imaging, non-destructive testing, and flexible displays.

2. The method for preparing the X-ray responsive polymer phosphorescent scintillator according to claim 1, characterized in that: The specific synthetic route and free radical polymerization process of halogenated monomers are as follows: ； X is a halogen atom Br.

3. The method for preparing the X-ray responsive polymer phosphorescent scintillator according to claim 1, characterized in that: The substitution reaction is carried out under KOH / DMF conditions; Step (2) involves heating and refluxing toluene as a solvent under a nitrogen atmosphere to carry out free radical polymerization.

Images