Methyl 4-hydroxybenzoate organic single crystal as well as preparation method and application thereof

Abstract

The invention discloses a methyl 4-hydroxybenzoate organic single crystal as well as a preparation method and application thereof, and relates to the technical field of organic crystals. The method comprises the following steps: uniformly dispersing a methyl 4-hydroxybenzoate polycrystal material in acetone, and then filtering to remove impurities and insoluble substances to obtain a filtered solution; and standing the filtered solution at 0-5 DEG C for 12-48 hours to obtain the methyl 4-hydroxybenzoate organic single crystal. According to the invention, a low-temperature solvent evaporation method is combined with a low-temperature seed crystal method, so that the problems of poor crystal quality, small crystal size, complex process and high equipment requirement in the existing 4MHB crystal growth are effectively solved, and the large-size and high-quality 4MHB single crystal growth is realized.

Description

Technical Field

[0001] The invention relates to the technical field of organic crystals, and in particular to a 4-hydroxybenzoic acid methyl ester organic single crystal and a preparation method and application thereof. Background Art

[0002] In recent years, the application of fast neutron detection technology in the fields of nuclear energy, radiation protection, and medical imaging has attracted widespread attention. However, existing neutron detectors still face some challenges, especially in the need for efficient and accurate detection of fast neutrons. Fast neutron detection usually relies on the interaction between materials and neutrons, and is achieved by detecting secondary particles (such as recoil protons, electrons, etc.). Ideal detection materials should have high hydrogen density, low dark current, good charge carrier mobility, fast response speed, and high radiation stability.

[0003] Organic semiconductor materials have shown great application potential in the field of radiation detection, especially in fast neutron detection, due to their advantages such as high hydrogen density and low manufacturing cost. Methyl 4-hydroxybenzoate (4MHB) is a new type of organic semiconductor material with a high hydrogen density (2×10 22 n cm -3 ), showing excellent performance in fast neutron detection. In addition, 4MHB single crystal has a high carrier mobility (μ = 15.62 cm 2 ·V -1 ·s -1 ) and low dark current (less than 10 at 100 V -12 A), and also has good radiation stability, showing great potential as a fast neutron detection material.

[0004] Increasing the size of 4MHB single crystals helps to improve neutron detection efficiency, but usually as the size of the single crystal increases, internal defects will also increase, thus affecting the electrical transport performance. At present, common 4MHB single crystal growth methods include the Czochralski method, physical vapor transport (PVT) method, slow cooling method and solvent evaporation method. Although the Czochralski method can grow single crystals with a maximum diameter of 25 mm, the crystal quality is poor and cannot meet the requirements of high-performance detectors. The PVT method has high requirements for the control of growth conditions, complex equipment operation, long growth cycle, and it is difficult to stably grow large-size, high-quality single crystals; the slow cooling method successfully grew a 45×42×62 mm single crystal by suspending seed crystals. 3 Large-sized single crystals can be produced by the solvent evaporation method, but crystal defects are easily generated during the cooling process, resulting in low crystal quality. The solvent evaporation method uses acetone as a solvent to grow centimeter-level single crystals at room temperature. Although larger-sized single crystals can be obtained, their quality has significant problems, with many macroscopic defects and an ultraviolet transmittance of less than 70%, failing to meet high quality standards.

[0005] Therefore, in order to realize the wide application of 4MHB single crystals in fields such as fast neutron detection, it is urgent to develop a method for stably growing large-size, high-quality 4MHB single crystals. Summary of the invention

[0006] In view of the deficiencies in the above-mentioned background technology, the present invention mainly solves the problems of low crystal quality, small crystal size, complex process and high requirements for crystal growth equipment in the existing 4MHB crystal growth process. The present invention provides a 4-hydroxybenzoic acid methyl ester organic single crystal and a preparation method and application thereof. The method effectively overcomes the problems of poor crystal quality and uncontrollable growth through a low-temperature solvent volatilization method and a low-temperature seed crystal method, and realizes the growth of large-size and high-quality 4MHB single crystals.

[0007] The first object of the present invention is to provide a method for preparing an organic single crystal of methyl 4-hydroxybenzoate, comprising the following steps: The methyl 4-hydroxybenzoate polycrystalline material is uniformly dispersed in acetone, and then filtered to remove impurities and insoluble matter to obtain a filtered solution; The filtered solution is allowed to stand at 0-5°C for 12-48 hours to obtain an organic single crystal of methyl 4-hydroxybenzoate.

[0008] Preferably, the usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 2.0-2.5 g: 10-15 mL.

[0009] Preferably, the filtered solution is sealed with a sealing membrane, and after holes are opened in the sealing membrane, the solution is allowed to stand.

[0010] Preferably, the usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 8.85-9.0 g: 30-32 mL.

[0011] Preferably, the filtered solution is sealed and then allowed to stand; After standing, it also includes: A defect-free seed crystal is selected and fixed at the bottom of the container, the static solution is injected, and the container is sealed with a sealing film, and the container is placed in the growth device again to obtain a large-sized methyl 4-hydroxybenzoate organic single crystal.

[0012] Preferably, during filtration, an organic filter head with a pore size of 0.22 μm is used to filter the solution to remove impurities and insoluble matter.

[0013] Preferably, the methyl 4-hydroxybenzoate polycrystalline material is obtained by purifying the methyl 4-hydroxybenzoate powder raw material three times, and each purification step comprises: soaking the methyl 4-hydroxybenzoate raw material in petroleum ether, discarding the petroleum ether after shaking, heating it to 55-60° C. on a heating table, evaporating it to dryness, and then dissolving it in acetone and filtering, drying and recrystallizing it.

[0014] The second object of the present invention is to provide an organic single crystal of methyl 4-hydroxybenzoate, the ultraviolet-visible-near infrared light transmittance of the single crystal is as high as 90% in the band above 400 nm.

[0015] The third object of the present invention is to provide an application of a 4-hydroxybenzoic acid methyl ester organic single crystal in fast neutron detection.

[0016] Preferably, the organic single crystal of methyl 4-hydroxybenzoate is used to detect fast neutrons of different fluxes with a sensitivity of 6.19 cps·nv -1 .

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a 4-hydroxybenzoic acid methyl ester organic single crystal and a preparation method and application thereof. The present invention uses acetone as a solvent. Acetone has a moderate solubility, can effectively control the stacking of crystal grains, and has a fast volatilization rate, so that it is easy to accurately control the crystal growth process, and finally realize the efficient preparation of large-size, high-quality single crystals. Compared with the prior art, the growth method of the present invention is simple and economical to operate, and can obtain single crystals with excellent performance while reducing production costs.

[0018] The present invention adopts a solvent volatilization method combined with a low-temperature seed crystal method, and adjusts the solution to a near-saturated state to dissolve part of the surface of the seed crystal. At this time, the seed crystal serves as a template to promote uniform growth of the crystal. The defects caused by excessively high nucleation rate or excessively fast growth rate in the traditional method are effectively avoided, thereby ensuring the stable growth of the crystal, and finally obtaining high-quality large-size 4MHB single crystals.

[0019] In addition, the detector made based on this has great potential in the field of radiation detection. It can not only effectively detect neutrons, but also has excellent fast neutron energy recognition ability. Experimental and simulated spectra have verified that it has a good response to neutron sources and a high linear response to neutrons with different fluxes. Its sensitivity reaches 6.19 cps·nv -1 , which can be used for fast neutron flux testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the growth process of 4MHB crystal.

[0021] Figure 2 A constant temperature ice water bath device for seed crystal growth.

[0022] Figure 3 It is a seed crystal and a single crystal after growth.

[0023] Figure 4 4MHB crystals grown under different conditions: (a) 0℃, 0.20g / ml; (b) 30℃, 0.20g / ml; (c) 15℃, 0.20g / ml; (d) -5℃, 0.20g / ml; (e) 0℃, 0.10g / ml; (f) 0℃, 0.30g / ml.

[0024] Figure 5 This is the UV-visible-near-infrared transmission spectrum of 4MHB single crystal.

[0025] Figure 6 This is the X-ray diffraction pattern of 4MHB single crystal.

[0026] Figure 7 Experimental neutron spectrum of 4MHB detector: (a) background spectrum, α particle spectrum and neutron spectrum under the same test conditions; (b) comparison between simulated spectrum and experimental spectrum.

[0027] Figure 8 The linear response characterization results of the 4MHB detector. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0029] The present invention provides a preparation method and application of large-sized methyl 4-hydroxybenzoate (4MHB) organic semiconductor single crystals grown by a low-temperature solvent volatilization method combined with a low-temperature seed crystal method, aiming to solve the problems of poor crystal quality, small crystal size, complex process and high equipment requirements in the existing 4MHB crystal growth. By regulating the saturation state, temperature and volatilization rate of the solution, the method successfully realizes the preparation of large-sized, high-quality 4MHB single crystals. Based on the single crystal, direct detection of fast neutrons is successfully realized, showing excellent energy recognition ability and linear response ability, and providing a new technical solution for the field of fast neutron detection.

[0030] The present invention realizes the growth of large-sized and high-quality 4MHB single crystals by combining a low-temperature solvent volatilization method with a low-temperature seed crystal method. The method comprises dissolving 4MHB polycrystalline material in acetone and filtering it, and then obtaining a large-sized single crystal by volatilization crystallization under low-temperature conditions and seed crystal induced growth. The detector made based on the 4MHB single crystal has good energy recognition ability and linear response in fast neutron detection, and the sensitivity is as high as 6.19 cps·nv-1 .

[0031] The first aspect of the present invention provides a method for preparing an organic single crystal of methyl 4-hydroxybenzoate, comprising the following steps: The methyl 4-hydroxybenzoate polycrystalline material is uniformly dispersed in acetone, and then filtered to remove impurities and insoluble matter to obtain a filtered solution; The filtered solution is allowed to stand at 0-5°C for 12-48 hours to obtain an organic single crystal of methyl 4-hydroxybenzoate.

[0032] Wherein, the usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 2.0-2.5 g: 10-15 mL.

[0033] The filtered solution is sealed with a sealing film, and after a hole is opened in the sealing film, it is allowed to stand.

[0034] According to the present invention, the usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 8.85-9.0 g: 30-32 mL.

[0035] The filtered solution is sealed and then allowed to stand; after standing, the following steps are also included: A defect-free seed crystal is selected and fixed at the bottom of the container, the static solution is injected, and the container is sealed with a sealing film, and the container is placed in the growth device again to obtain a large-sized methyl 4-hydroxybenzoate organic single crystal.

[0036] During filtration, an organic filter head with a pore size of 0.22 μm was used to filter the solution to remove impurities and insoluble matter.

[0037] The 4-hydroxybenzoic acid methyl ester (4MHB) polycrystalline material is obtained by purifying the 4-hydroxybenzoic acid methyl ester powder raw material three times, and each purification step includes: soaking the 4-hydroxybenzoic acid methyl ester raw material in petroleum ether, discarding the petroleum ether after shaking, heating it to 55-60° C. on a heating table, evaporating it to dryness, then dissolving it in acetone and filtering, drying and recrystallizing it.

[0038] The purification process specifically includes: weighing 20-25 g of methyl tetrahydroxybenzoate powder raw material with a purity of ≥99.0%, soaking it fully with petroleum ether (AR≥99.0%), shaking it for 20 seconds, pouring out the petroleum ether, and placing the raw material on a heating table, heating it at 55-60°C for 10 minutes, evaporating it and drying it. Then, measuring 100-120 mL of acetone with a purity of AR≥99.7% as a solvent, adding the raw material to the acetone, and completely dissolving it by magnetic stirring, followed by filtering, drying and recrystallization.

[0039] Exemplarily, a method for preparing an organic single crystal of methyl 4-hydroxybenzoate comprises: Weigh 2.0-2.5 g of 4MHB polycrystalline material, add 10-15 mL of acetone, and stir with a magnetic stirrer until 4MHB is completely dissolved; The solution was filtered using an organic filter head with a pore size of 0.22 μm to remove impurities and insoluble matter to obtain a filtered solution; Wrap the filtered solution with plastic wrap and tie it tightly with a rubber band, poke two small holes, and place it in a refrigerator for 36 to 48 hours to allow the acetone to evaporate slowly and the solution to gradually reach a supersaturated state. 4MHB crystals will precipitate in this process.

[0040] The refrigerator temperature is 0-5° C. to ensure that the solution evaporates slowly during the standing process and promote the effective growth of crystals.

[0041] Exemplarily, a method for preparing an organic single crystal of methyl 4-hydroxybenzoate comprises: Weigh 8.85-9.0 g of 4MHB polycrystalline material, add 30-32 mL of acetone, and stir with a magnetic stirrer until 4MHB is completely dissolved; The solution was filtered using an organic filter head with a pore size of 0.22 μm to remove impurities and insoluble matter; Transfer the filtered solution to a sealed container and place it in a refrigerator to keep warm for 12 to 16 hours; the insulation temperature is 0 to 5°C; A defect-free seed crystal was selected, fixed at the bottom of the beaker, the insulated solution was slowly injected, and it was quickly sealed with a sealing film and placed in the growth device again, finally obtaining a large-sized and high-quality 4MHB single crystal.

[0042] The filtration step after the magnetic stirring is performed by combining a syringe booster and an organic filter tip to ensure that impurities and insolubles in the solution are completely removed.

[0043] The temperature of the refrigerator is set at 0~5℃ to ensure that the solution evaporates slowly during the standing process and promote the effective growth of crystals.

[0044] A second aspect of the present invention provides a 4-hydroxybenzoic acid methyl ester organic single crystal, the ultraviolet-visible-near infrared light transmittance of the single crystal is as high as 90% in the band above 400 nm.

[0045] Among them, the molecular formula of 4MHB organic crystal is C8H8O3, and the structural formula is: .

[0046] The third aspect of the present invention provides an application of methyl 4-hydroxybenzoate organic single crystal in fast neutron detection. The methyl 4-hydroxybenzoate organic single crystal is used to detect fast neutrons of different fluxes with a sensitivity of 6.19 cps·nv-1 The 4MHB single crystal is used for direct detection of fast neutrons and has excellent energy recognition capability and linear response capability.

[0047] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0048] Example 1 See also Figure 1 As shown, a method for preparing methyl 4-hydroxybenzoate seed crystals comprises the following steps: S1. Raw material preparation and preliminary processing: Weigh 20 g of methyl 4-hydroxybenzoate (4MHB) powder raw material with a purity of AR ≥ 99.0%. Soak the raw material in petroleum ether (purity AR ≥ 99.0%), shake for about 20 seconds, and then discard the petroleum ether. Heat the raw material on a heating table at a temperature of 55-60°C for about 10 minutes until the solvent in the raw material is evaporated, and then dry it.

[0049] S2. Solution configuration: Measure 100 mL of acetone with a purity of AR ≥ 99.7% as a solvent, add the preliminarily treated raw material into the acetone, and stir with a magnetic stirrer until the raw material is completely dissolved.

[0050] S3, first filtration: After stirring, the solution was filtered through a syringe booster combined with a 0.22 μm organic filter tip to remove impurities and insoluble matter in the solution to obtain a pure solution after the first filtration.

[0051] S4, recrystallization operation: The solution after the first filtration was wrapped with two layers of plastic wrap and tied with a rubber band to make three small holes. The solution was left to evaporate at room temperature for 24 hours to obtain the crystals after the first recrystallization. The crystals after the first recrystallization were repeated with the above dissolution and filtration steps (using the same amount of acetone and the same filtration method) to obtain the solution before the second recrystallization. The solution before the second recrystallization was subjected to a second recrystallization operation to obtain the crystals after the second recrystallization. The crystals after the second recrystallization were repeated with the above dissolution and filtration steps to obtain the solution before the third recrystallization.

[0052] S5, low temperature volatile crystallization: The recrystallized solution was divided into ten portions, each portion was placed in a beaker and wrapped with two layers of plastic wrap. The plastic wrap was tied tightly with a rubber band and two small holes were punched in the plastic wrap. The beakers were placed in a 0°C refrigerator for 48 hours. During this period, the acetone slowly evaporated under low temperature conditions, causing crystals to precipitate. Figure 4As shown in (a), the size is about 5×4×2 mm 3 The obtained single crystal can be used as a seed crystal for subsequent crystal growth.

[0053] Among them, an ice water bath is used to maintain a constant temperature. The equipment consists of a glass water tank, a mercury thermometer and a beaker stand. Figure 2 Place it in a refrigerator set at 0°C, continuously test the temperature of the ice-water bath with a mercury thermometer, and keep adding ice cubes to keep the temperature constant.

[0054] Example 2 See also Figure 1 As shown, a method for preparing a large-sized single crystal of methyl 4-hydroxybenzoate comprises the following steps: S1. Solution preparation: Weigh 8.85 g of 4MHB crystals that meet the purity requirements and put them into a clean and dry beaker. Measure 30 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the raw materials are completely dissolved to form a uniform mixed solution.

[0055] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to let the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0056] S3, insulation: The filtrate was quickly transferred to a well-sealed dedicated container and placed in a growth device to keep warm for 12 hours.

[0057] S4. Seed crystal implantation and solution injection: The selected seed crystals were glued to the bottom of the beaker, the insulated solution was slowly injected into the beaker and quickly sealed with a sealing film, and then placed in a growth device at 0°C.

[0058] S5. Crystal growth: Under the above conditions, due to the slight dissolution of the seed crystal, the solution reaches a saturated state. The solute in the solution will gradually grow with the seed crystal as the core, with the help of the existing crystal nucleus. After 24 hours, the maximum size of the harvested crystal is 20×15×10mm. 3 High quality 4MHB single crystal. Figure 3 (b) shows the seed crystal and the single crystal after growth.

[0059] Comparative Example 1 S1. Solution preparation: Weigh 0.20 g of 4MHB crystals that meet the purity requirements and place them in a clean, dry beaker. Measure 10 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the crystals are completely dissolved to obtain a uniform solution with a concentration of 0.20 g / ml.

[0060] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to make the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0061] S3, volatile crystallization: Wrap the beaker with two layers of plastic wrap and tie it tightly with a rubber band, and poke two small holes in the plastic wrap. Place the beaker in a 30°C water bath and let it stand for 36 hours. During this period, the acetone evaporates, the solution gradually reaches a supersaturated state, and crystals begin to precipitate. Figure 4 As shown in (b).

[0062] Comparative Example 2 S1. Solution preparation: Weigh 0.20 g of 4MHB crystals that meet the purity requirements and place them in a clean, dry beaker. Measure 10 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the crystals are completely dissolved to obtain a uniform solution with a concentration of about 0.20 g / ml.

[0063] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to make the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0064] S3, volatile crystallization: Wrap the beaker with two layers of plastic wrap and tie it tightly with a rubber band, and poke two small holes in the plastic wrap. Place the beaker in a 15°C water bath for 36 hours. During this period, the acetone evaporates, the solution gradually reaches a supersaturated state, and crystals begin to precipitate. Figure 4 As shown in (c).

[0065] Comparative Example 3 S1. Solution preparation: Weigh 0.20 g of 4MHB crystals that meet the purity requirements and place them in a clean, dry beaker. Measure 10 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the crystals are completely dissolved to obtain a uniform solution with a concentration of about 0.20 g / ml.

[0066] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to make the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0067] S3, volatile crystallization: Wrap the beaker with two layers of plastic wrap and tie it tightly with a rubber band, and poke two small holes in the plastic wrap. Place the beaker in a -5°C refrigerator for 48 hours. During this period, acetone evaporates slowly at low temperatures, the solution gradually reaches a supersaturated state, and crystals begin to precipitate. Figure 4 As shown in (d).

[0068] Comparative Example 4 S1. Solution preparation: Weigh 0.10 g of 4MHB crystals that meet the purity requirements and place them in a clean, dry beaker. Measure 10 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the crystals are completely dissolved to obtain a uniform solution with a concentration of about 0.10 g / ml.

[0069] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to make the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0070] S3, volatile crystallization: Wrap the beaker with two layers of plastic wrap and tie it tightly with a rubber band, and poke two small holes in the plastic wrap. Place the beaker in a 0℃ growth device and let it stand for 36 hours. During this period, the acetone evaporates, the solution gradually reaches a supersaturated state, and crystals begin to precipitate. Figure 4 As shown in (e).

[0071] Comparative Example 5 S1. Solution preparation: Weigh 0.30 g of 4MHB crystals that meet the purity requirements and place them in a clean, dry beaker. Measure 10 mL of acetone with a purity of AR ≥ 99.7% and add it to the beaker. Stir with a magnetic stirrer until the crystals are completely dissolved to obtain a uniform solution with a concentration of about 0.30 g / ml.

[0072] S2. Filtering: Select an organic filter head with a pore size of 0.22 μm and install it correctly on the filter device to ensure no leakage. Slowly pour the solution and use the pressure difference to make the solution pass through the filter head to intercept impurities and insoluble matter to obtain pure filtrate.

[0073] S3, volatile crystallization: Wrap the beaker with two layers of plastic wrap and tie it tightly with a rubber band, and poke two small holes in the plastic wrap. Place the beaker in a 0℃ growth device and let it stand for 36 hours. During this period, the acetone evaporates, the solution gradually reaches a supersaturated state, and crystals begin to precipitate. Figure 4 As shown in (f).

[0074] In order to illustrate the relevant performances of the 4MHB single crystal provided by the present invention, it is described in conjunction with the accompanying drawings.

[0075] Figure 1 The process flow for growing methyl 4-hydroxybenzoate (4MHB) crystals covers multiple steps from raw material preparation, dissolution and filtration, recrystallization operation to seed crystal growth. First, petroleum ether is mixed with 4MHB raw materials, and then they are washed and dried; then, 4MHB is dissolved in acetone by magnetic stirring and filtered; then, the crystals are purified by volatile crystallization and three recrystallizations; finally, large-sized single crystals are obtained by seed crystal growth. During the whole process, the temperature is strictly controlled at 0°C to ensure the quality and efficiency of crystal growth.

[0076] Figure 2 Schematic diagram of the ice-water bath thermostat for low-temperature seed crystal growth, including a glass water tank, a mercury thermometer, and a beaker stand. The device is placed in a refrigerator set at 0°C. The mercury thermometer continuously monitors the temperature and ice cubes are added regularly to maintain a constant temperature.

[0077] Figure 3 The seed crystal (a) grown by the low-temperature solvent evaporation method in Example 1 and the centimeter-scale large-size single crystal (b) grown in Example 2 are shown in FIG. 1 , 1 , and 2 .

[0078] Figure 4Figure 4MHB crystals grown under different conditions: (a) 0℃, 0.20g / ml; (b) 30℃, 0.20g / ml; (c) 15℃, 0.20g / ml; (d) -5℃, 0.20g / ml; (e) 0℃, 0.10g / ml; (f) 0℃, 0.30g / ml. The growth of 4MHB single crystals shows significant differences under different temperature and concentration conditions. Under 30℃, 0.20 g / ml, the evaporation rate of the solution is fast, resulting in rapid precipitation of solutes, uncontrollable nucleation number, poor crystal quality, and easy formation of clusters. At 15℃, 0.20 g / ml, the crystal growth is relatively stable, with fewer nuclei and moderate size, but the crystal is not transparent and of poor quality. Under -5℃, 0.20 g / ml, the crystal grows slowly, and defects appear inside the large-sized single crystals, affecting the permeability. As for the effect of concentration, at 0℃ and 0.10 g / ml, the crystal size is small and the growth is slow; at 0℃ and 0.20 g / ml, the crystal size is moderate, the quality is good, and the crystallization is uniform; while at 0℃ and 0.30 g / ml, the crystals are crowded, the grain boundaries increase, and the quality is poor. In summary, at 0℃ and 0.20 g / ml, the crystal growth is most ideal, the size is moderate, and the quality is good.

[0079] Figure 5 This is the UV-Vis-NIR spectrum of the 4MHB single crystal in Example 2. Figure 5 (a) shows that the light transmittance of 4MHB single crystal in the band above 400nm is as high as 90%, indicating that it has excellent crystal quality. Figure 5 (b) is 4MHB with a bandgap of 4.12 eV.

[0080] Figure 6 This is the X-ray diffraction spectrum of the 4MHB single crystal in Example 2. After comparing the position and intensity with the simulated spectrum, it can be seen that the maximum exposed plane is the {021} crystal plane.

[0081] Figure 7 Experimental neutron spectrum of the 4MHB detector made in Example 2: Figure 7 (a) shows the neutron energy spectrum of the 4MHB detector (chemical source, 10.8 MeV), and compares it with the background noise and alpha source (5.5 MeV) spectrum. Under the same test conditions, the highest channel address of the measured alpha particle energy spectrum is 2240. After calculation, the channel address corresponding to the alpha particle with an energy of 10.8 MeV is 4400, and the highest channel address obtained by actual measurement is 4500. The two values ​​are very close, which verifies the accurate response of the 4MHB detector to different particle energies. The neutron energy spectrum is concentrated in the range of 1000 to 4000 channels, and the average count of each channel is greater than 100, which fully demonstrates the excellent response performance of the detector to neutrons. Figure 7(b) further verifies that the 4MHB detector has good response characteristics to neutrons by comparing the experimental spectrum with the simulated spectrum, further confirming its application potential in fast neutron detection.

[0082] Figure 8 These are the experimental results used to characterize the linear response capability of the 4MHB detector made in Example 2. Figure 8 (a) For different fluxes of 2.5 MeV neutrons emitted by the neutron tube, the measured neutron energy spectrum counts vary significantly. As the neutron flux increases, the energy spectrum always maintains a typical rectangular shape without distortion. Figure 8 (b) After the total counts of the energy spectrum at different fluxes are counted and linearly fitted, a good linear relationship is clearly shown, with a sensitivity of 6.19 cps·nv -1 .

[0083] In summary, the present invention provides a 4MHB single crystal preparation process and its application in the field of fast neutron detection. A low-temperature solvent evaporation method combined with a seed crystal method is used to grow large-sized single crystals. Compared with some existing technologies, this method does not require complex equipment and harsh environments, and can effectively avoid the problems of poor crystal quality and uncontrollable growth in existing technologies. The detector made based on this can effectively detect neutrons and has excellent fast neutron energy recognition capabilities. Experimental and simulated spectra verify that it responds well to neutron sources. It has good linear response to neutrons with different fluxes, and the sensitivity is 6.19 cps·nv -1 , which can be used for fast neutron flux testing and has great potential in the field of radiation detection.

[0084] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an organic single crystal of methyl 4-hydroxybenzoate, characterized in that: The following steps are involved: The methyl 4-hydroxybenzoate polycrystalline material is uniformly dispersed in acetone, and then filtered to remove impurities and insoluble matter to obtain a filtered solution; The filtered solution is allowed to stand at 0-5°C for 12-48 hours to obtain an organic single crystal of methyl 4-hydroxybenzoate.

2. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 1, characterized in that: The usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 2.0-2.5 g: 10-15 mL.

3. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 2, characterized in that: The filtered solution is sealed with a sealing film, and after a hole is opened in the sealing film, it is allowed to stand.

4. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 1, characterized in that: The usage ratio of the methyl 4-hydroxybenzoate polycrystalline material to the acetone is 8.85-9.0 g: 30-32 mL.

5. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 4, characterized in that: The filtered solution is sealed and then allowed to stand; After standing, it also includes: A defect-free seed crystal is selected and fixed at the bottom of the container, the static solution is injected, and the container is sealed with a sealing film, and the container is placed in the growth device again to obtain a large-sized methyl 4-hydroxybenzoate organic single crystal.

6. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 1, characterized in that: During filtration, an organic filter head with a pore size of 0.22 μm was used to filter the solution to remove impurities and insoluble matter.

7. The method for preparing an organic single crystal of methyl 4-hydroxybenzoate according to claim 1, characterized in that: The methyl 4-hydroxybenzoate polycrystalline material is obtained by purifying the methyl 4-hydroxybenzoate powder raw material three times, and each purification step includes: soaking the methyl 4-hydroxybenzoate raw material in petroleum ether, discarding the petroleum ether after shaking, heating it to 55-60° C. on a heating table, evaporating it to dryness, then dissolving it in acetone and filtering, drying and recrystallizing it.

8. An organic single crystal of methyl 4-hydroxybenzoate obtained by the method according to any one of claims 1 to 7, characterized in that: The UV-visible-near-infrared light transmittance of this single crystal is as high as 90% in the band above 400 nm.

9. Use of the methyl 4-hydroxybenzoate organic single crystal according to claim 8 in fast neutron detection.

10. Use of the methyl 4-hydroxybenzoate organic single crystal in fast neutron detection according to claim 9, characterized in that: Organic single crystals of methyl 4-hydroxybenzoate were used to detect fast neutrons of different fluxes with a sensitivity of 6.19 cps·nv -1 .

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