Perovskite liquid scintillator and application thereof

Abstract

The invention discloses a liquid scintillator prepared from a CsPbBr3 perovskite nanocrystal and an application of the liquid scintillator in X-ray imaging. In the process of synthesizing CsPbBr3 perovskite nanocrystals by adopting a thermal injection method, the perovskite nanocrystals are modified by introducing interaction of dodecylbenzene sulfonic acid (serving as a long ligand) and cyanamide (serving as a short ligand), and the perovskite nanocrystals are effectively dispersed in an n-hexane solvent, so that the liquid scintillator is prepared. The liquid scintillator can show the change of crystal morphology, the photoluminescence intensity is obviously improved, the luminescence center is subjected to blue shift, the radiation luminescence intensity is enhanced, and meanwhile, the high radiation stability is kept. X-rays can be utilized to excite the liquid scintillator to emit light, and a light-emitting image is captured and recorded through a camera, so that high-resolution X-ray imaging can be successfully realized.

Description

Technical Field

[0001] The present invention belongs to the field of X-ray imaging, and specifically relates to a liquid scintillator prepared by dispersing CsPbBr3 perovskite nanocrystals passivated by dodecylbenzenesulfonic acid (DBSA) and monocyanamide (H2NCN) in a non-polar solvent medium, and its application in X-ray imaging. Background Art

[0002] Nuclear radiation detection plays a vital role in high-energy physics experiments, oil drilling and exploration, medical imaging, and homeland security. Compared with semiconductor detectors, scintillators have the advantage of converting X-rays, gamma rays, etc. into visible light or ultraviolet light, which can better meet general needs. Therefore, scintillators have now become a key element in the interaction between X-rays and imaging detectors.

[0003] With the development of imaging nuclear medicine medical equipment and the increasing demand for high-energy physics and nuclear physics experiments, the demand for scintillators is getting higher and higher. They must have key factors such as high effective atomic number, high light yield, fast decay, and low cost. However, due to the manufacturing process and inherent limitations, commercial solid-state scintillators cannot meet the above characteristics at the same time. Traditional liquid scintillators have excellent resistance to radiation damage, highly flexible scalability, fast decay time, and low cost, and are mainly used for beta-ray and neutrino detection. However, the relatively low atomic number and moderate light yield are crucial to achieving high resolution and contrast in X-ray imaging, which hinders the further application of liquid scintillators.

[0004] In the past few decades, people have tried to solve the above problems by loading high atomic number organometallic compounds or nanoparticles into liquid scintillators or plastic scintillators. Due to the strong spin-orbit coupling effect, it remains a challenge to find soluble organometallic compounds that do not destroy the stability and radioactive physical properties of liquid scintillators. As an alternative, researchers have developed nanocomposite scintillators to increase the solubility of atomic number materials. The previous use of nanoparticles (CdSe / ZnS quantum dots) for radiation detection has opened up a new path for composite scintillators. However, the resulting CdSe / ZnS quantum dots have a small Stokes shift, which will lead to photon reabsorption and a decrease in quantum yield.

[0005] In recent years, perovskite nanocrystals have become promising candidates for radiation detection due to their excellent properties such as highly emissive X-ray-generated exciton states, ultrafast radiative emission rates, resistance to high-energy radiation, high radiative luminescence quantum yields, and fast decay times. This material has strong X-ray absorption and can efficiently convert radiation photons into visible photons. At the same time, unlike bulk perovskites, perovskite nanocrystals can be processed in solutions at relatively low temperatures and costs, and are uniformly dispersed in non-polar liquid media, making them suitable for liquid scintillators. Summary of the invention

[0006] The relatively low atomic number and medium light yield of traditional liquid scintillators have hindered the further application of liquid scintillators in X-rays. The purpose of the present invention is to provide a liquid scintillator prepared by using CsPbBr3 perovskite nanocrystals, and use it for X-ray imaging, which is achieved by combining CsPbBr3 perovskite nanocrystals with DBSA (long ligand) and H2NCN (short ligand) to change the morphology of the perovskite nanocrystals, enhance the photoluminescence intensity, blue-shift the luminescence center, and enhance the radiation luminescence intensity, thereby achieving X-ray imaging.

[0007] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: A perovskite liquid scintillator based on CsPbBr3 is prepared by using dodecylbenzenesulfonic acid (DBSA) as a long ligand and monocyanamide (H2NCN) as a short ligand to passivate CsPbBr3 perovskite nanocrystals together and then dispersing them in a non-polar solvent medium.

[0008] The preparation of the perovskite liquid scintillator comprises the following steps: 1) Preparation of Cs-DBSA precursor: Cs2CO3, DBSA and n-octadecane (ODE) were mixed, heated at 150 °C for 30 min, and then condensed and stirred at 120 °C in a nitrogen atmosphere (purity 99.99%) to obtain a Cs-DBSA precursor solution; 2) Preparation of CsPbBr3 perovskite nanocrystals: PbBr2 and ODE were mixed and kept at 120 °C in vacuum for 1 h. Then, oleic acid (OA) and oleylamine (OAm) were added in a nitrogen atmosphere to accelerate the dissolution of PbBr2. The mixture was heated to 180 °C and the Cs-DBSA precursor solution obtained in step 1) was quickly injected and reacted for 3 seconds. The reaction mixture was placed in an ice water bath and cooled to terminate the growth of CsPbBr3 to obtain a crude solution containing CsPbBr3 perovskite nanocrystals. 3) Ligand doping and purification of CsPbBr3: Ethyl acetate was added to the crude solution obtained in step 2) and mixed, and then the mixture was centrifuged at 7500 rpm for 10 min, and the supernatant containing excess ligand and unreacted by-products was discarded; then the precipitate was dispersed in n-hexane, and a mixture of H2NCN and ethyl acetate was added, and centrifuged again at 7500 rpm for 10 min; the purified precipitate was dispersed in n-hexane and stored in a refrigerator.

[0009] Furthermore, the molar ratio of Cs2CO3, PbBr2, DBSA, and H2NCN used in the operation is 0.9:0.4:3.6:0.36.

[0010] Furthermore, the volume ratio of ODE, OA and OAm used in step 2) is 20:1:1.

[0011] Furthermore, in step 3), the volume ratio of the crude solution to ethyl acetate is 1:1.

[0012] The obtained perovskite liquid scintillator prepared based on CsPbBr3 can be used in X-ray imaging.

[0013] The significant advantages of the present invention are: (1) The present invention combines CsPbBr3 perovskite nanocrystals with DBSA (long ligand) and H2NCN (short ligand) to obtain an improved perovskite nanocrystal liquid scintillator, whose crystal morphology has changed, the photoluminescence intensity has increased, the luminescence center has blue-shifted, and the radiant luminescence intensity has also increased. This may be due to (1) a strong quantum size effect; (2) the dual ligands stabilize CsPbBr3. It can be used for X-ray imaging, which can achieve imaging at multiple angles and can also be customized for different containers for imaging.

[0014] (2) The present invention has important guiding significance for the design and synthesis of scintillators and can promote the development of nuclear radiation detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a transmission electron microscope image (TEM) of the CsPbBr3 perovskite nanocrystal scintillator prepared in Example 1.

[0016] Figure 2 This is a photoluminescence spectrum of the CsPbBr3 perovskite nanocrystal scintillator prepared in Example 1.

[0017] Figure 3 This is the radiation luminescence spectrum of the CsPbBr3 perovskite nanocrystal scintillator prepared in Example 1.

[0018] Figure 4This is a graph showing the relationship between the radiation luminescence intensity and the number of cycles of the CsPbBr3 perovskite nanocrystal liquid scintillator in Example 2.

[0019] Figure 5 This is a diagram showing the radiation luminescence intensity of the CsPbBr3 perovskite nanocrystal liquid scintillator in Example 2 in relation to the radiation angle.

[0020] Figure 6 This is a relationship diagram between the X-ray dose and the luminescence intensity of the CsPbBr3 perovskite nanocrystal liquid scintillator in Example 2.

[0021] Figure 7 This is a diagram showing the result of X-ray imaging using CsPbBr3 perovskite nanocrystal liquid scintillator in Example 3. DETAILED DESCRIPTION

[0022] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0023] Example 1 Synthesis of CsPbBr3 Perovskite Nanocrystalline Liquid Scintillator ① Add Cs2CO3 (0.292 g, 0.9 mmol), DBSA (1.2 g, 3.6 mmol) and ODE (10 mL) into a 50 mL three-necked flask, heat to 150 °C, keep for 30 minutes, and then condense and stir at 120 °C under nitrogen flow to prepare a Cs-DBSA precursor solution; wherein the concentration of DBSA is 0.36 mmol / mL and the concentration of Cs is 0.18 mmol / mL; ② Take PbBr2 (0.1468 g, 0.4 mmol) and ODE (20 mL) and place them in a 50 mL three-necked flask, place it in a vacuum, and gradually increase the temperature to 120 °C. After keeping it for 1 hour, place the flask in a nitrogen atmosphere, and inject OA (1 mL) and OAm (1 mL) into the three-necked flask to accelerate the dissolution of PbBr2; then increase the temperature to 180 °C, and quickly inject the Cs-DBSA precursor solution heated to 120 °C. After reacting for 3 seconds, the reaction mixture is placed in an ice water bath to cool to terminate the growth of CsPbBr3 and obtain a crude solution containing CsPbBr3 perovskite nanocrystals.

[0024] ③ Collect the obtained crude solution into a 50 mL centrifuge tube, add ethyl acetate as an anti-solvent at a volume ratio of 1:1, centrifuge the mixture at 7800 rpm for 10 min, discard the supernatant containing excess ligand and unreacted by-products, then disperse the precipitate in 6 mL of n-hexane, take 1 ml and add it to a mixture of different masses (0~25 mg) of cyanamide and 1 mL of ethyl acetate, and centrifuge it again at 7500 rpm for 10 min; the purified precipitate is the CsPbBr3 perovskite nanocrystal scintillator, which is dispersed in 2 ml of n-hexane and collected in a clean and dry vial, and then stored in a refrigerator; at the same time, use a syringe and needle to collect the supernatant containing the final sample.

[0025] Depend on Figure 1 Transmission electron microscopy images of CsPbBr3 perovskite nanocrystal scintillators show that their nanoparticles are in a cubic phase.

[0026] Depend on Figure 2 From the photoluminescence spectrum of CsPbBr3 perovskite nanocrystal scintillator, it can be seen that with the increase of H2NCN dosage, its luminescence intensity first increases and then decreases, among which the luminescence intensity of 15 mg is the highest.

[0027] Depend on Figure 3 From the radiant luminescence spectrum of CsPbBr3 perovskite nanocrystal scintillator, it can be seen that with the increase of H2NCN dosage, its radiant luminescence intensity first increases and then decreases, among which the radiant luminescence intensity of 15 mg is the highest.

[0028] Example 2 Related Tests of Radioluminescence 0.5 ml of the CsPbBr3 perovskite nanocrystal scintillator solution prepared in Example 1 was taken and its stability was tested using an external X-ray fluorescence spectrometer. The results are shown in Figure 4 .Depend on Figure 4 It can be seen that the addition of H2NCN and DBSA ligands makes the obtained perovskite nanocrystal liquid scintillator have better radiation stability.

[0029] 0.5 ml of the CsPbBr3 perovskite nanocrystal scintillator solution prepared in Example 1 was taken and the relationship between the radiation angle and intensity was tested using an external X-ray fluorescence spectrometer. The results are shown in Figure 5 .Depend on Figure 5 It can be seen that the material has a test radiation intensity at nearly all angles.

[0030] 0.5 ml of the CsPbBr3 perovskite nanocrystal scintillator solution prepared in Example 1 was taken and the luminescence intensity was tested under different doses of X-ray using an external X-ray fluorescence spectrometer. The results are shown in Figure 6 .Depend on Figure 6It can be seen that the X-ray dose and luminous intensity are positively correlated.

[0031] Example 3 X-ray imaging related tests 0.5 ml of the CsPbBr3 perovskite nanocrystal scintillator solution prepared in Example 1 was injected into a cuvette, and the chip, capsule with a spring and other materials were used as imaging objects. X-ray imaging was performed by placing the imaging object between the X-ray light source and the cuvette. The results are shown in FIG. Figure 7 .Depend on Figure 7 It can be seen that under X-ray irradiation (30 kV, 300 μA), the scintillator material in the cuvette can emit visible light photons, thereby leaving pattern information; after the X-ray irradiation stops, the pattern on the imaging film can be digitally recorded and stored as an image by setting reasonable exposure parameters with a digital camera (due to the different materials and thicknesses of various parts of the imaging object, there are significant differences in the X-ray energy received by the imaging film).

[0032] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A perovskite liquid scintillator prepared based on CsPbBr3, characterized in that: The perovskite liquid scintillator is prepared by first using dodecylbenzenesulfonic acid as a long ligand and monocyanamide as a short ligand to jointly passivate CsPbBr3 perovskite nanocrystals, and then dispersing the CsPbBr3 perovskite nanocrystals in a non-polar solvent medium.

2. The perovskite liquid scintillator according to claim 1, characterized in that: Its preparation comprises the following steps: 1) Preparation of Cs-DBSA precursor: Cs2CO3, dodecylbenzenesulfonic acid and n-octadecane were mixed, heated at 150 °C for 30 min, and then condensed and stirred at 120 °C in a nitrogen atmosphere to obtain a Cs-DBSA precursor solution; 2) Preparation of CsPbBr3 perovskite nanocrystals: PbBr2 and n-octadecane were mixed and kept at 120°C for 1h in vacuum, then oleic acid and oleylamine were added in a nitrogen atmosphere for dissolution, and then the temperature was raised to 180°C, and the Cs-DBSA precursor solution obtained in step 1) heated to 120°C was quickly injected. After reacting for 3s, the reaction mixture was placed in an ice water bath for cooling to terminate the growth of CsPbBr3, thereby obtaining a crude solution containing CsPbBr3 perovskite nanocrystals; 3) Ligand doping and purification of CsPbBr3: Ethyl acetate was added to the crude solution obtained in step 2) and mixed, and then the mixture was centrifuged at 7500 rpm for 10 min and the supernatant was discarded; then the precipitate was dispersed in n-hexane, and a mixture of cyanamide and ethyl acetate was added, and centrifuged again at 7500 rpm for 10 min; the purified precipitate was dispersed in n-hexane and stored in a refrigerator.

3. The perovskite liquid scintillator according to claim 2, characterized in that: The molar ratio of Cs2CO3, PbBr2, dodecylbenzenesulfonic acid and cyanamide used in the operation is 0.9:0.4:3.6:0.

36.

4. The perovskite liquid scintillator according to claim 2, characterized in that: In step 3), the volume ratio of the crude solution to ethyl acetate is 1:

1.

5. An application of the perovskite liquid scintillator prepared based on CsPbBr3 as claimed in claim 1 in X-ray imaging.

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