Blue light scintillator material and preparation method and application thereof

Abstract

The invention relates to the field of photoelectric device materials, in particular to a blue light scintillator material and a preparation method and application thereof. A trace amount of Pb < 2 + > ions are doped in AnZnBr4 with relatively weak luminous intensity to serve as an optical active center, so that the absorption coefficient and exciton binding energy of the halide material can be improved, and the luminous property and scintillation property of the halide are further improved. An AnZnBr4: Pb zero-dimensional halide containing different organic groups is assembled by using a simple and convenient low-temperature wet chemical method, and the maximum emission wavelength, the half-peak width and the color purity of the AnZnBr4: Pb zero-dimensional halide are adjustable. Compared with low luminous activity of original zinc halide, trace Pb < 2 + > doping significantly promotes formation of STEs, improves emission efficiency of the STEs, obtains excellent scintillation response, has ultrahigh structural stability and spectral stability, realizes high-performance underwater X-ray imaging, and has broad application prospects. The technical problem that an existing blue light-emitting material is difficult to apply to an underwater environment is solved.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic device materials, and particularly to a blue light scintillator material, a preparation method thereof, and an application thereof. Background Art

[0002] The ocean covers about 71% of the Earth's surface. Underwater imaging technology is crucial in scientific research, economic, and military applications such as marine resource exploration, military communication, archaeology, mineral detection, and maritime rescue. Compared with acoustic and microwave imaging, optical imaging has the ability to obtain more intuitive and higher-resolution images, especially X-ray imaging technology based on scintillators. Among the entire visible light wavelength range, blue light sources have the lowest attenuation coefficient, absorption, and scattering in seawater, and the strongest penetration ability in the deep sea. At the same time, blue light scintillators have unique advantages in assembling photodetectors in cooperation with photomultiplier tubes. Therefore, exploring underwater blue light scintillators with high luminous efficiency and strong water resistance stability is of great significance for seabed detection.

[0003] In the past few decades, three-dimensional lead perovskite CsPbX3 (X = Cl, Br, I) has become the most concerned luminescent material in light-emitting diodes and display technologies due to its high photoluminescence quantum yield (PLQY), high color purity, and tunable emission wavelength in all visible spectral ranges. In particular, three-dimensional perovskites can also absorb high-energy X-ray photons to produce low-energy visible radio luminescence (RL). However, compared with the nearly unit PLQYs of green and red light emissions, due to the small exciton binding energy of CsPbCl3 (~50 MeV), its blue light emission efficiency is relatively low (<5%), not to mention having high-performance scintillation characteristics. Therefore, blue light emission has always been the most challenging problem in the entire optical field.

[0004] To improve the luminescence efficiency, another effective approach is to reduce the structural dimension of the anion framework and construct low-dimensional metal halides (LDMHs). However, due to the large Stokes shift generated by self-trapped excitons (STE), most LDMHs tend to exhibit low-energy light emission from green to red, hindering the generation of high-energy blue light emission. So far, only a small number of Cu(I)-based or doped LDMHs can produce blue light emission under X-ray excitation, including 0D Cs3Cu2I5, 1D Rb2CuX3 (x = Cl, Br), and 1D Cs5Cu3Cl6I2. However, due to Cu + being extremely easy to oxidize in the atmosphere, almost all Cu(I)-based or doped LDMHs have serious spectral instability problems in the aqueous phase. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art, and provides a blue light scintillator material, a preparation method and an application thereof, solving the technical problem that the existing blue light emitting materials are difficult to be applied to the underwater environment.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a blue light scintillator material, and the chemical general formula of the blue light scintillator material is A n ZnBr4:Pb, where n is 1 to 2, A is an organic group, and the mass proportion of Pb in the blue light scintillator material is 0.4% to 3.8%.

[0008] Optionally, the organic group is any one of heptyltriphenylphosphonium cation, (4-fluorobenzyl)triphenylphosphonium cation, triphenylbenzylphosphonium cation, N,N'-dicyclohexyl-4-morpholineamidine cation, (1-pentyl)triphenylphosphonium cation, ethoxycarbonylmethyltriphenylphosphonium cation, 1-isopropylpiperazine cation, 4-bromobenzyltriphenylphosphonium cation and propyltriphenylphosphonium cation.

[0009] The present invention provides a preparation method of the above blue light scintillator material, including the following steps:

[0010] Using zinc bromide, lead bromide and an organic compound with a mass ratio of 3 to 4:1:3 to 4 as raw materials, in a solvent system, through a solvothermal reaction, lead is doped to obtain A n ZnBr4:Pb. The organic compound is a quaternary phosphonium salt compound or a nitrogen-containing heterocyclic compound.

[0011] Optionally, the reaction temperature of the solvothermal reaction is 70°C to 85°C, and the reaction time is 4d to 6d.

[0012] Optionally, the quaternary phosphonium salt compound is any one of heptyltriphenylphosphonium bromide, (4-fluorobenzyl)triphenylphosphonium bromide, triphenylbenzylphosphonium bromide, (1-pentyl)triphenylphosphonium bromide, ethoxycarbonylmethyltriphenylphosphonium bromide, 4-bromobenzyltriphenylphosphonium bromide and propyltriphenylphosphonium bromide.

[0013] Optionally, the nitrogen-containing heterocyclic compound is N,N'-dicyclohexyl-4-morpholineamidine or 1-isopropylpiperazine.

[0014] Optionally, the solvent system is ethylene glycol and hydrobromic acid with a volume ratio of 4:1.

[0015] The present invention provides an application of a composite film made of the above blue light scintillator material in the preparation of an underwater X-ray imaging device.

[0016] Optionally, the preparation method of the composite film includes the following steps:

[0017] In the cyclohexane system, the blue scintillator material and ethylene-vinyl acetate copolymer are mixed and stirred evenly at a mass ratio of 1:10 to form a mixed solution, and a composite film is prepared on the surface of the mold by spin coating.

[0018] The beneficial effect of the present invention is that, compared with the prior art, by doping trace amounts of Pb 2+ ions as optical active centers, the absorption coefficient and exciton binding energy of a series of halide A n ZnBr4 materials can be improved, demonstrating the universality of this strategy. Using a simple low-temperature wet chemical method, A n ZnBr4:Pb zero-dimensional halides containing different organic groups are assembled, and their maximum emission wavelength (416 nm - 472 nm), full width at half maximum (46 nm - 89 nm), and color purity (69% - 97%) are all adjustable. Compared with the low luminescence activity of the original zinc halide, the doping of trace amounts of Pb 2+ significantly promotes the formation of STEs and improves their emission efficiency, obtaining excellent scintillation response. Among them, (HTPP)Zn2Br4:Pb has the best scintillation luminescence performance, with a light yield of 31500 ph·meV -1 , a detection limit of 134.8 nGy·s -1 , and a spatial resolution of 15.10 lp / mm for X-ray imaging. It has ultra-high structural stability and spectral stability, highlighting the wide application of blue scintillators in the underwater world, realizing high-performance underwater X-ray imaging, and solving the technical problem that existing blue light-emitting materials are difficult to apply in underwater environments. Brief Description of the Drawings

[0019] Figure 1 Schematic diagram of the crystal structure change of (HTPP)Zn2Br4 and Pb 2+ after doping.

[0020] Figure 2 For (HTPP)Zn2Br4 and Pb 2+ Powder X-ray diffraction pattern after doping.

[0021] Figure 3 Element distribution map of (HTPP)Zn2Br4:Pb. Among them, a) is the scanning electron microscope image of (HTPP)Zn2Br4:Pb, b) is the element distribution map of Zn, c) is the element distribution map of Pb, d) is the element distribution map of Br, e) is the element distribution map of C, and f) is the element distribution map of P.

[0022] Figure 4 For (HTPP)Zn2Br4 and Pb 2+XPS spectrum of Pb element after doping.

[0023] Figure 5 For (HTPP)Zn2Br4 and Pb 2+ UV-Vis absorption spectrum after doping.

[0024] Figure 6 Is the band gap of (HTPP)Zn2Br4.

[0025] Figure 7 Is the band gap of (HTPP)Zn2Br4:Pb.

[0026] Figure 8 For (HTPP)Zn2Br4 and Pb 2+ Emission and excitation spectra after doping.

[0027] Figure 9 For (HTPP)Zn2Br44 and Pb 2+ CIE coordinate diagram after doping.

[0028] Figure 10 For (HTPP)Zn2Br4 and Pb 2+ Comparison diagram of PLQY after doping.

[0029] Figure 11 For (HTPP)Zn2Br4 and Pb 2+ Comparison diagram of lifetimes after doping.

[0030] Figure 12 For zero-dimensional Zn halides with different structures and Pb 2+ Luminescence photos of doped halides under 365 nm light excitation.

[0031] Figure 13 For zero-dimensional Zn halides with different structures and Pb 2+ Statistical chart of quantum yields of doped halides.

[0032] Figure 14 Is the luminescence photo of (HTPP)Zn2Br4:Pb in water.

[0033] Figure 15 Is the luminescence photo of (HTPP)Zn2Br4:Pb in different chemical species.

[0034] Figure 16 Is the luminescence photo of (HTPP)Zn2Br4:Pb in different organic solvents.

[0035] Figure 17 Is the luminescence photo of (HTPP)Zn2Br4:Pb in natural water quality.

[0036] Figure 18 For (HTPP)Zn2Br4 and Pb 2+ Statistical chart of the light yield after doping.

[0037] Figure 19 Emission spectra of (HTPP)Zn2Br4:Pb at different radiation doses.

[0038] Figure 20 Linear relationship diagram of different radiation doses and luminescence intensity of (HTPP)Zn2Br4:Pb.

[0039] Figure 21 Relationship diagram of the afterglow time and luminescence intensity of (HTPP)Zn2Br4:Pb.

[0040] Figure 22 Characterization diagram of the radiation stability of (HTPP)Zn2Br4:Pb within 140 minutes.

[0041] Figure 23 Luminescence photo of (HTPP)Zn2Br4:Pb@EVA film.

[0042] Figure 24 Flexibility display diagram of (HTPP)Zn2Br4:Pb@EVA film.

[0043] Figure 25 X-ray imaging photo of (HTPP)Zn2Br4:Pb@EVA film. Among them, a) is the photo of the physical object, and b) is the X-ray imaging photo.

[0044] Figure 26 Resolution characterization diagram of (HTPP)Zn2Br4:Pb@EVA film. Among them, a) is the resolution characterization diagram, and b) is the partial enlarged schematic diagram of the framed area in Figure a).

[0045] Figure 27 Statistical chart of the MTF results of (HTPP)Zn2Br4:Pb@EVA film.

[0046] Figure 28 Stability test diagram of (HTPP)Zn2Br4:Pb@EVA film under continuous radiation in water.

[0047] Figure 29 Display diagram of the underwater imaging test system of (HTPP)Zn2Br4:Pb@EVA film.

[0048] Figure 30 Imaging photos of (HTPP)Zn2Br4:Pb@EVA film in pure water and natural water quality. Among them, a) is the imaging photo in pure water, and b) is the imaging photo in natural water quality. Detailed implementation mode

[0049] To solve the above technical problems, the present invention provides a zero-dimensional zinc halide perovskite material, a preparation method thereof and an application. The technical solutions and embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0050] The present invention will be described in detail below through specific embodiments. The embodiments are exemplary and are intended to explain the present invention, and should not be construed as a limitation of the present invention.

[0051] Reagents and materials:

[0052] Materials: Zinc bromide (ZnBr2, Aladdin, 99%), lead bromide (PbBr2, Aladdin, 99%), heptyltriphenylphosphonium bromide (HTPPBr, Aladdin, 99%), (1-pentyl)triphenylphosphonium bromide (PTPPBr, Aladdin, 99%), (4-fluorobenzyl)triphenylphosphonium bromide, ((4-F)BzTPPBr, Aladdin, 99%), benzyltriphenylphosphonium bromide (BzTPPBr, Aladdin, 99%), N,N'-dicyclohexyl-4-morpholinecarboxamidine, (DCHMM, Macklin, 98%), 1-isopropylpiperazine, ((i-Pr)PiPz, Macklin, 98%), ethoxycarbonylmethyltriphenylphosphonium bromide, ((COMTPP)Br, Macklin, 98%), 4-bromobenzyltriphenylphosphonium bromide, ((4-Br)BzTPPBr, Aladdin, 99%), propyltriphenylphosphonium bromide, (PrTPPBr, Aladdin, 99%), hydrobromic acid (HBr, Macklin, 99%), ethanol (EtOH, Macklin, 99%), ethylene glycol (Macklin, 98%), poly(ethylene-vinyl acetate) (EVA, Aladdin), cyclohexane (Macklin, 99%). All chemical materials and solvents are commercially available and can be used without further purification.

[0053] Example 1

[0054] This example provides a preparation method of (HTPP)2ZnBr4:Pb@EVA film, including the following steps:

[0055] Step 1, synthesis of (HTPP)2ZnBr4:Pb.

[0056] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and (HTPP)Br (0.08 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, blocky colorless crystals were obtained with a yield of 77%. The doping amount of lead measured by ICP was 2.5%.

[0057] In this study, the preparation methods of other undoped zero-dimensional Zn halides and Pb-doped 2+ zero-dimensional Zn halides are similar to the preparation methods of (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb, except that the corresponding organic ligands are used to replace (HTPP)Br.

[0058] Step 2: Preparation of (HTPP)2ZnBr4:Pb@EVA film.

[0059] 2.0 g of EVA was completely dissolved in 5 mL of cyclohexane, stirred at 60 °C for 1 h to form a solution, and then 1 mL of a cyclohexane solution of 0.2 g / mL (HTPP)2ZnBr4:Pb was added to the above solution under stirring until a homogeneous viscous fluid was formed. The flexible film was prepared by rapid spin coating on a glass mold and slowly evaporated at room temperature in a fume hood.

[0060] Example 2

[0061] This example provides a preparation method of ((4-F)BzTPP)2ZnBr4:Pb, including the following steps:

[0062] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and (4-F)BzTPPBr (0.22 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, blocky colorless crystals were obtained with a yield of 73%. The doping amount of lead measured by ICP was 0.45%.

[0063] Example 3

[0064] This example provides a preparation method of (BzTPP)2ZnBr4:Pb, including the following steps:

[0065] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and BzTPPBr (0.23 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 72%. The doping amount of lead measured by ICP was 1.2%.

[0066] Example 4

[0067] This example provides a preparation method of (DCHMM)2ZnBr4:Pb, including the following steps:

[0068] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and DCHMM (0.34 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 63%. The doping amount of lead measured by ICP was 0.7%.

[0069] Example 5

[0070] This example provides a preparation method of (PTPP)2ZnBr4:Pb, including the following steps:

[0071] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and PTPPBr (0.24 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 68%. The doping amount of lead measured by ICP was 0.7%.

[0072] Example 6

[0073] This example provides a preparation method of (COMTPP)ZnBr4:Pb, including the following steps:

[0074] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and COMTPPBr (0.23 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, blocky colorless crystals were obtained with a yield of 59%. The doping amount of lead measured by ICP was 1.9%.

[0075] Example 7

[0076] This example provides a method for preparing ((i-Pr)PiPz)2ZnBr4:Pb, which includes the following steps:

[0077] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and (i-Pr)PiPz (0.60 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, blocky colorless crystals were obtained with a yield of 52%. The doping amount of lead measured by ICP was 0.4%.

[0078] Example 8

[0079] This example provides a method for preparing ((4-Br)BzTPP)2ZnBr4:Pb, which includes the following steps:

[0080] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and (4-Br)BzTPPBr (0.23 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, blocky colorless crystals were obtained with a yield of 74%. The doping amount of lead measured by ICP was 0.7%.

[0081] Example 9

[0082] This example provides a method for preparing (PrTPP)2ZnBr4:Pb, which includes the following steps:

[0083] A mixture of ZnBr2 (0.44 mmol, 0.10 g), PbBr2 (0.08 mmol, 0.03 g) and PrTPPBr (0.33 mmol, 0.10 g) was dissolved in ethylene glycol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. Then the solution was sealed in a glass bottle and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 79%. The doping amount of lead measured by ICP was 3.8%.

[0084] Comparative Example 1

[0085] This comparative example provides a preparation method of ((4-F)BzTPP)2ZnBr4, including the following steps:

[0086] A mixture of ZnBr2 (0.44 mmol, 0.10 g) and (HTPP)Br (0.08 mmol, 0.10 g) was dissolved in ethanol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. The solution was sealed in a glass vial and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 86%.

[0087] Comparative Example 2

[0088] This comparative example provides a preparation method of ((4-F)BzTPP)2ZnBr4, including the following steps:

[0089] A mixture of ZnBr2 (0.44 mmol, 0.10 g) and (4-F)BzTPPBr (0.22 mmol, 0.10 g) was dissolved in ethanol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. The solution was sealed in a glass vial and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 82%.

[0090] Comparative Example 3

[0091] This comparative example provides a preparation method of (BzTPP)2ZnBr4, including the following steps:

[0092] A mixture of ZnBr2 (0.44 mmol, 0.10 g) and BzTPPBr (0.23 mmol, 0.10 g) was dissolved in ethanol (4 mL) and hydrobromic acid (1 mL), and stirred for 10 min to obtain a homogeneous solution. The solution was sealed in a glass vial and heated at 80 °C for 5 days. After cooling to room temperature, colorless block crystals were obtained with a yield of 69%.

[0093] Comparative Example 4

[0094] This comparative example provides a method for preparing (DCHMM)2ZnBr4, which includes the following steps:

[0095] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and DCHMM (0.34 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 56%.

[0096] Comparative Example 5

[0097] This comparative example provides a method for preparing (PTPP)2ZnBr4, which includes the following steps:

[0098] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and PTPPBr (0.24 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 73%.

[0099] Comparative Example 6

[0100] This comparative example provides a method for preparing (COMTPP)ZnBr4, which includes the following steps:

[0101] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and COMTPPBr (0.23 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 63%.

[0102] Comparative Example 7

[0103] This comparative example provides a method for preparing ((i-Pr)PiPz)2ZnBr4, which includes the following steps:

[0104] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and (i-Pr)PiPz (0.60 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 56%.

[0105] Comparative Example 8

[0106] This comparative example provides a method for preparing ((4-Br)BzTPP)2ZnBr4, which includes the following steps:

[0107] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and (4-Br)BzTPPBr (0.23 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 76%.

[0108] Comparative Example 9

[0109] This comparative example provides a method for preparing (PrTPP)2ZnBr4, which includes the following steps:

[0110] Dissolve a mixture of ZnBr2 (0.44 mmol, 0.10 g) and PrTPPBr (0.33 mmol, 0.10 g) in ethanol (4 mL) and hydrobromic acid (1 mL), stir for 10 min to obtain a homogeneous solution. Seal the solution in a glass vial and heat it at 80 °C for 5 days. After cooling to room temperature, block-shaped colorless crystals were obtained with a yield of 82%.

[0111] Structure characterization tests:

[0112] (1) X-ray diffraction

[0113] X-ray single crystal data of the synthesized metal halide were collected using a Bruker Apex II CCD diffractometer equipped with Mo-Kα radiation (wavelength ).

[0114] (2) Powder X-ray diffraction

[0115] Characterization was carried out on a Bruker D8 ADVANCE.

[0116] (3) Ultraviolet-visible absorption spectroscopy

[0117] Using a PE Lambda 900 ultraviolet-visible spectrophotometer, the ultraviolet-visible absorption spectrum was collected with BaSO4 powder as the reflectance reference.

[0118] Luminescence performance tests:

[0119] (1) Photoluminescence characterization

[0120] The photoluminescence (PL) spectrum was obtained using a Hitachi F-7000 fluorescence spectrometer. The photoluminescence quantum yield was measured by equipping an integrating sphere in an FLS5 fluorescence spectrophotometer.

[0121] (2) Radioluminescence Characterization

[0122] A fluorescence spectrometer model 1000 with an X-ray tube was used to obtain the radioluminescence (RL) spectrum. The X-ray source is a silver target X-ray tube with the following parameters: maximum power: 10 W; maximum voltage: 50 kV; maximum current: 200 μA; X-ray photon energy: 22 keV. A Hamamatsu R928 photomultiplier tube was used to collect the X-ray response intensity. The X-ray dose rate was calibrated by a high-sensitivity X-ray ionization chamber dosimeter (type 10×5 - 180 from Raycal Corporation).

[0123] Analysis of Test Results

[0124] (1) Crystal Structure Analysis

[0125] Single-crystal X-ray diffraction analysis shows that the (HTPP)2ZnBr4 crystal belongs to the monoclinic system P21 / n. Each Zn atom coordinates with four Br atoms to form a slightly distorted [ZnBr4] 2- tetrahedron, and these tetrahedrons are further separated and surrounded by (HTPP) + cations to form a typical periodically arranged zero-dimensional hybrid structure ( Figure 1 ). The nearest Zn···Zn distance between the halide structures is indicating no electronic interaction between adjacent [ZnBr4] 2- tetrahedrons. The powder X-ray diffraction (PXRD) pattern of (HTPP)2ZnBr4 is in good agreement with the single-crystal structure simulation data, indicating a high sample purity. After Pb 2+ doping, no phase transition and impurities were observed in the PXRD pattern, showing the same crystal structure as (HTPP)2ZnBr4 ( Figure 2 ). Elemental mapping of energy-dispersive spectroscopy (EDS) reveals the uniform distribution of C, P, Br, Zn, and Pb elements on the surface of the A x ZnBr4:Pb crystal, indicating that Pb was successfully introduced into the (HTPP)2ZnBr4 lattice ( Figure 3 ). At the same time, the presence of Pb element was confirmed by X-ray photoelectron spectroscopy (XPS), and Pb-4f 7 / 2 and -4f 5 / 2 were observed at 138.5 and 142.6 eV respectively, further proving the successful doping of Pb 2+ ions ( Figure 4 ).

[0126] (2) Photoluminescence Property Analysis

[0127] To study the photophysical properties of (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb, the ultraviolet-visible absorption spectra were recorded. AsFigure 5 As shown, the absorption spectrum of (HTPP)2ZnBr4 shows strong absorption below 275 nm, with an obvious absorption edge and indirect bandgap characteristics. Pb 2+ After Pb doping, the sample has a wide absorption range from 303 nm to 431 nm. Among them, the main peak at 320 nm is due to the absorption of the 5s orbital transition of Pb 2+ ions, while the main peak at 375 nm is the absorption peak of free excitons at the band edge.

[0128] According to the Tauc function, the bandgaps of (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb are calculated to be 3.98 eV and 2.75 eV respectively, indicating that the introduction of Pb 2+ ions leads to a decrease in the bandgap ( Figure 6 and Figure 7 ). Under 365 nm ultraviolet light irradiation, both colorless samples show blue luminescence, but the luminescence intensity of Pb 2+ -doped (HTPP)2ZnBr4 is significantly stronger than that of undoped Pb 2+ -doped (HTPP)2ZnBr4, indicating the significant contribution of Pb 2+ as a photosensitizer ( Figure 5 inset).

[0129] Subsequently, their photoluminescence properties were studied by steady-state and time-resolved spectroscopy. As Figure 8 shown, two main excitation peaks are observed for both (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb, with maximum wavelengths of 365 nm and 283 nm respectively. Under 365 nm ultraviolet light excitation, both (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb show narrow-band blue light emission centered at 430 nm wavelength, and their CIE chromaticity coordinates are almost the same, (0.159, 0.057) and (0.156, 0.033) respectively, indicating that Pb 2+ directly participates in the original radiative recombination pathway rather than acting as a new emission center ( Figure 9 ). The results show that the PLQY of (HTPP)2ZnBr4:Pb is as high as 65.69%, much larger than the low emission efficiency (12.83%) of (HTPP)2ZnBr4 ( Figure 10 ). The applicant further recorded the time-resolved PL decay curves, and the average lifetimes of (HTPP)2ZnBr4 and (HTPP)2ZnBr4:Pb were obtained as 0.136 μs and 0.144 μs respectively by double-exponential fitting ( Figure 11 ). The slightly longer lifetime of (HTPP)2ZnBr4:Pb is consistent with the increase in PLQY, which may be due to the incorporation of Pb 2+The non-radiative recombination rate after ions is weakened. Based on the large Stokes shift (65 nm) and long lifetime, the applicant speculates that the above blue light emission may be triplet self-trapped excitons caused by electron-phonon coupling effects in the zero-dimensional structure of the soft lattice, which is similar to most reported zero-dimensional zinc halides.

[0130] (3) Verification of general doping strategy

[0131] The successful optimization of the luminescence efficiency of (HTPP)2ZnBr4 inspired the applicant to further extend this doping strategy to other zero-dimensional Zn halides. As a proof of concept, the applicant also used this strategy to design a series of other zero-dimensional Zn halides based on [ZnBr4] 2- tetrahedra and various organic cations ((4-F)BzTPP)2ZnBr4, (BzTPP)2ZnBr4, (DCHMM)2ZnBr4, (PTPP)2ZnBr4, (COMTPP)ZnBr4, ((i-Pr)PiPz)2ZnBr4, ((4-Br)BzTPP)2ZnBr4, (PrTPP)2ZnBr4), and used Pb 2+ doping strategy to improve their luminescence efficiency.

[0132] In Figure 12 , under 365 nm ultraviolet light, the photos of the pristine undoped (upper) and Pb 2+ doped (lower) Zn 2+ -based LDMHs show blue light emission. Compared with the original zinc halide, all Pb 2+ -doped samples can emit brighter blue light. Through the measurement of PLQYs, the improvement of luminescence efficiency was clearly confirmed. As Figure 13 shown, compared with the undoped zinc halide, the PLQYs of Pb 2+ -doped Zn-based OIMHs all increased significantly, which is consistent with the observed luminescence photos. Most importantly, the luminescence rate of ((4-f)BZTPP)2ZnBr4 increased from negligible (0.1%) to nearly unity PLQY (93.5%), demonstrating the feasibility of Pb 2+ doping as an effective strategy to improve the luminescence efficiency of zero-dimensional Zn-based LDMHs. The above results indicate that Pb 2+ doping is an effective and general method to improve the blue light emission efficiency of zero-dimensional Zn halides.

[0133] (4) Stability study

[0134] Considering the severe instability of zero-dimensional halide perovskites due to their weak ionic nature, taking (HTPP)2ZnBr4:Pb as an example, the water resistance stability of the synthesized samples was further investigated. The results showed that (HTPP)2ZnBr4:Pb had ultra-high water resistance stability. As Figure 14 shown, the (HTPP)2ZnBr4:Pb crystals could still emit bright blue light after being continuously immersed in deionized water for 6 months. Inspired by its ultra-high stability in water, the applicant further studied the stability of (HTPP)2ZnBr4:Pb in more complex chemical environments. As Figure 15 and Figure 16 shown, (HTPP)2ZnBr4:Pb could still emit strong blue light in various inorganic aqueous solutions and organic solvents, even in mixed solutions with a pH range of 1 to 14. In addition, the applicant also evaluated the stability of the compound in the natural waters of Taibai Lake and Liaohe near the laboratory. As Figure 17 shown, the samples dispersed in natural water still showed bright blue light emission, demonstrating that they could also maintain stability in natural water quality. The excellent structural and spectral stability of zero-dimensional Zn metal halides in various extreme environments makes them have broad application prospects in multiple complex fields, especially in underwater environments.

[0135] (5) Analysis of Radioluminescence Performance and X-ray Imaging Applications

[0136] Considering the high PLQY, water resistance stability, and applications in photodetectors, the X-ray-excited radioluminescence was further studied. As Figure 18 shown, taking the commercial LuAG:Ce as a standard sample, the light yield of (HTPP)2ZnBr4:Pb was measured to be 31,500 ph·MeV -1 , which was significantly higher than that of the undoped sample and exceeded the highest value of all previously reported zinc-based halides. The RL intensity at different dose rates was further recorded, showing a linear response in the range of 5000 μGy air ·s -1 ~50000 μGy air ·s -1 , indicating the possibility of high-dose applications ( Figure 19 and Figure 20 ). In addition, the detection limit could be obtained by extracting the RL intensity at low dose rates. As Figure 20 shown in the inset, the detection limit of (HTPP)2ZnBr4:Pb was 134.8 nGy air ·s -1 , much lower than the 5.5 μGy air ·s -1 required for X-ray medical diagnosis.。Considering that too long afterglow time can lead to low-contrast imaging, severe image lag or ghosting, in order to evaluate its potential application in X-ray imaging, the afterglow lifetime of (HTPP)2ZnBr4:Pb was measured. As Figure 21 shown, within 10.09 ms after the X-ray stopped, the RL intensity rapidly decreased to zero, showing negligible image ghosting and high imaging contrast. Radiation stability is another important parameter for evaluating scintillation performance, and its stability was tested by recording the RL intensity under continuous on / off X-ray irradiation for more than 10 times. After continuous irradiation for more than 140 minutes, the RL intensity had a negligible decay, indicating robust stability against high-energy radiation ( Figure 22 ). These results indicate that (HTPP)2ZnBr4:Pb has potential application prospects as a high-performance X-ray scintillator.

[0137] Flexible scintillation screens can closely adhere to non-planar objects, achieving high imaging contrast and resolution on curved or complex surfaces of detection targets. In this case, (HTPP)2ZnBr4:Pb was mixed with EVA to fabricate a (HTPP)2ZnBr4:Pb@EVA flexible screen with a size of approximately 5.8 cm × 4.2 cm.

[0138] As Figure 23 shown, the flexible film emits bright blue light under ultraviolet light irradiation. In addition, the film has excellent flexibility, can be bent arbitrarily, and the blue light emission is stable ( Figure 24 ). Subsequently, the X-ray imaging of the (HTPP)2ZnBr4:Pb@EVA film was evaluated using a self-made X-ray imaging system.

[0139] As Figure 25 shown, the internal structure of the circuit board can be clearly distinguished under X-ray irradiation, revealing the ability of X-ray imaging. Since the quality of X-ray imaging is mainly evaluated by resolution, the spatial resolution of (HTPP)2ZnBr4:Pb was measured using an X-ray standard test pattern panel, and the observable resolution limit was approximately 14 - 16 lp·mm -1 ( Figure 26 ).

[0140] Furthermore, the modulation transfer function (MTF) curve was quantitatively obtained using the slanted edge method to evaluate the spatial resolution. As Figure 27 shown, the spatial resolution of the (HTPP)2ZnBr4:Pb film was 15.10 lp·mm when the MTF was 0.2 -1, which is consistent with the observation results. The advantages such as high light yield, low detection limit, strong X-ray resistance, and excellent X-ray imaging performance prove that (HTPP)2ZnBr4:Pb is an ideal scintillator and has great application potential in medical or industrial X-ray imaging, non-destructive testing, underwater detection, etc.

[0141] Due to the advantages of good visualization, fast response, high precision, and non-destructiveness, the waterproof scintillation performance is crucial for underwater detection. However, due to the weak ionic bond nature, almost all reported metal halide-based scintillators are severely unstable in water, so almost all metal halide-based scintillators are limited to anhydrous applications. Given the excellent stability of (HTPP)2ZnBr4:Pb in various aqueous solutions, the X-ray imaging performance of the sample was tested in aqueous solutions using a self-made underwater X-ray imaging system.

[0142] First, the underwater stability of the flexible (HTPP)2ZnBr4:Pb@EVA film under X-ray irradiation was tested to verify the feasibility of the flexible (HTPP)2ZnBr4:Pb@EVA film for underwater X-ray imaging. As Figure 28 shown, after continuous X-ray irradiation with a total dose rate of 4.1 mG air ·s -1 , the radioluminescence intensity of the (HTPP)2ZnBr4:Pb@EVA film immersed in the aqueous solution still remained above 90% of the original level. The excellent stability of this halide in water indicates that it is an ideal waterproof scintillator for underwater X-ray imaging.

[0143] On this basis, the underwater imaging ability was evaluated by immersing the flexible screen and the object in water. Figure 29 Shows the photos of the object in the sealed tube under deionized water and sewage. As Figure 30 shown, in deionized water and sewage, the sealed spring can be clearly distinguished under X-ray irradiation, showing the unique advantages of underwater X-ray imaging, which is rarely achieved in metal halide scintillators. These results prove that these Pb 2+ -doped zero-dimensional zinc halides have good underwater X-ray imaging performance and have good application prospects in underwater resource exploration, rescue, and mineral detection, etc.

[0144] The above description is only the preferred embodiment of the present invention, and the above specific embodiments are not limitations to the present invention. Within the scope of the technical idea of the present invention, various deformations and modifications can occur. Any retouching, modification, or equivalent replacement made by those of ordinary skill in the art according to the above description shall fall within the scope protected by the present invention.

Claims

1. A blue light scintillator material, characterized in that, The chemical general formula of the blue light scintillator material is A n ZnBr4:Pb, where n is 1 to 2, A is an organic group, and the mass percentage of Pb in the blue light scintillator material is 0.4% to 3.8%.

2. The blue scintillator material according to claim 1, characterized in that, The organic group is any one of heptyltriphenylphosphonium cation, (4-fluorobenzyl)triphenylphosphonium cation, triphenylbenzylphosphonium cation, N,N'-dicyclohexyl-4-morpholine amidinium cation, (1-pentyl)triphenylphosphonium cation, ethoxycarbonylmethyltriphenylphosphonium cation, 1-isopropylpiperazinium cation, 4-bromobenzyltriphenylphosphonium cation, and propyltriphenylphosphonium cation.

3. A method for preparing the blue light scintillator material according to claim 1 or 2, characterized in that, It includes the following steps: Using zinc bromide, lead bromide, and an organic compound with a mass ratio of 3 to 4:1:3 to 4 as raw materials, in a solvent system, through a solvothermal reaction, lead is doped to obtain A n ZnBr4:Pb; The organic compound is a quaternary phosphonium salt compound or a nitrogen-containing heterocyclic compound.

4. The preparation method of the blue scintillator material according to claim 3, characterized in that, The reaction temperature of the solvothermal reaction is 70°C to 85°C, and the reaction time is 4d to 6d.

5. The preparation method of the blue scintillator material according to claim 3, characterized in that, The quaternary phosphonium salt compound is any one of heptyltriphenylphosphonium bromide, (4-fluorobenzyl)triphenylphosphonium bromide, triphenylbenzylphosphonium bromide, (1-pentyl)triphenylphosphonium bromide, ethoxycarbonylmethyltriphenylphosphonium bromide, 4-bromobenzyltriphenylphosphonium bromide, and propyltriphenylphosphonium bromide.

6. The preparation method of the blue scintillator material according to claim 3, characterized in that, The nitrogen-containing heterocyclic compound is N,N'-dicyclohexyl-4-morpholine amidine or 1-isopropylpiperazine.

7. The preparation method of the blue scintillator material according to claim 3, characterized in that, The solvent system is ethylene glycol and hydrobromic acid with a volume ratio of 4:

1.

8. Application of a composite film made of the blue light scintillator material described in claim 1 or 2 in the preparation of an underwater X-ray imaging device.

9. The application according to claim 8, characterized in that, The preparation method of the composite film includes the following steps: In a cyclohexane system, the blue scintillator material and ethylene-vinyl acetate copolymer are mixed and stirred evenly at a mass ratio of 1:10 to form a mixed solution, and a composite film is prepared on the surface of the mold by spin coating.

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