JP6590185B2 - Scintillator immobilized silicate particles - Google Patents

Description

  The present invention relates to scintillator-immobilized silicate particles and a radiation detection material using the same.

  In recent years, an imaging plate (IP) that enables two-dimensional imaging of radiation dose has attracted attention as a radiation detection material. However, at present, IP is very expensive and has a problem of quantification due to fading, attenuation of fluorescence amount, and the like. In addition, since IP requires a laser beam for detection, there is also a problem that measurement at a radioactive contamination site cannot be performed. Furthermore, once IP is contaminated with radioactive material, it becomes radioactive waste. This can be avoided by covering the IP with an antifouling film, but when detecting a sample such as tritium whose emitted radiation (β-rays) is low energy, it is difficult to detect if the film is covered with the film. Become. For this reason, when detecting a sample such as tritium, an expensive IP must be made disposable.

  On the other hand, the present inventor has developed a paper scintillator (Non-Patent Document 1) in which a scintillator (scintillator molecule-containing silica particles) (Patent Document 1, Non-Patent Document 1) is carried on paper as a radiation detection material. This paper scintillator is capable of two-dimensional imaging of the radiation dose, and can be manufactured at a lower cost than IP. Furthermore, the paper scintillator can easily detect radiation without requiring a laser beam for detection unlike IP.

Patent No. 4586191

Radiation Protection Dosimetry (2013), Vol.156, No.3, pp.277-282.

  It is an object of the present invention to provide a radiation detection material that can be produced at a lower cost and has a higher radiation detection sensitivity. In addition to this, another object of the present invention is to provide a radiation detection material capable of further two-dimensional imaging of the radiation dose and simpler radiation detection.

  As a result of diligent research in view of the above-mentioned problems, the present inventor uses silicic acid particles and scintillator immobilized on the surface of the particles, and uses scintillator-immobilized silicic acid particles as a material for a radiation detection material. The present inventors have found that the above problems can be solved. As a result of further research based on this finding, the present invention was completed.

  That is, the present invention includes the following aspects.

Item 1. A scintillator-immobilized silicic acid particle comprising silicic acid particles and a scintillator immobilized on the surface of the particles.
Item 2. Item 2. The scintillator-immobilized silicate particles according to Item 1, wherein the silicate particles have an average particle diameter of 0.1 to 100 µm.
Item 3. Item 3. The scintillator-immobilized silicate particle according to Item 1 or 2, wherein the silicate particle is a silica particle.
Item 4. Item 4. The scintillator-immobilized silicate particle according to any one of Items 1 to 3, wherein the scintillator is a silica nanoparticle containing an organic scintillator molecule.
Item 5. Item 5. The scintillator-immobilized silicate particles according to any one of Items 1 to 4, wherein the scintillator is fixed to the silicate particles via an adhesive.
Item 6. Item 6. A radiation detection material comprising the scintillator-immobilized silicate particles according to any one of Items 1 to 5 and a binder.
Item 7. Item 7. The radiation detection material according to Item 6, which is in the form of a sheet.
Item 8. Item 8. The radiation detection material according to Item 6 or 7, comprising a substance that enhances fluorescence emitted from a scintillator.

  The scintillator-immobilized silicate particles of the present invention have higher radiation detection sensitivity per fixed amount of scintillator compared to the case of a scintillator alone. Therefore, by using this as a material for the radiation detection material, the radiation detection material having the same or higher radiation detection sensitivity as that in the case of not reducing the usage amount while reducing the usage amount of the generally expensive scintillator. Can be obtained.

  The radiation detection material of the present invention can be manufactured at a lower cost than existing IP, can detect even low-energy radiation (for example, β-rays derived from tritium), and if used in the form of a sheet, the radiation can be detected. Two-dimensional imaging of quantities is also possible. In addition, since scintillator molecules are used, radiation can be easily detected without requiring a laser beam for detection as in the case of IP. Furthermore, since silicic acid particles are used as a carrier, even if it is contaminated, it is possible to enclose RI in a vitrified body by heating. Thereby, the expansion of contamination can be prevented.

An example of the fluorescence image of the sheet-like radiation detection material which dripped the solution containing a radioisotope is shown. The left side shows the position where each radioisotope was dropped, and the right side shows a fluorescence image. A black area represents a fluorescent area.

1. Scintillator-immobilized silicate particles The present invention relates to scintillator-immobilized silicate particles (referred to herein as “the scintillator-immobilized silica particles of the present invention”) containing silicic acid particles and a scintillator immobilized on the surface of the particles. Acid particles ”). The silicic acid particles can also be referred to as silicic acid particles having a scintillator immobilized on the surface, or silicic acid particles contained in a state where the scintillator is immobilized on the surface. This will be described below.

  The silicate particles are not particularly limited as long as they are particles containing silicon dioxide as a main component. The silicate particles contain silicon dioxide, for example, 70% by weight or more, preferably 75% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, still more preferably 90% by weight or more, and still more preferably. May be particles containing 95% by weight or more, more preferably 99% or more. Specifically, for example, silica particles can be used as the silicic acid particles.

  The average particle diameter of the silicic acid particles is not particularly limited, but can be, for example, about 0.1 to 100 μm. From the viewpoint of higher radiation detection sensitivity per fixed amount of scintillator, the average particle size of the silicate particles is preferably 0.5 to 50 μm, more preferably 1 to 30 μm, and even more preferably 1.5 to 20 μm, and more. More preferably, it is 2-15 micrometers, More preferably, it is 3-12 micrometers, More preferably, it is 4-9 micrometers, More preferably, it can be 4-7.5 micrometers.

  Silicate particles may be used singly or in combination of two or more.

  The scintillator is not particularly limited, and a scintillator molecule, a complex of scintillator molecules, and the like can be widely used. Among these, a complex of scintillator molecules is preferable.

  The scintillator molecule is not particularly limited, and known scintillator molecules such as organic scintillator molecules and inorganic scintillator molecules can be widely used. Of these, organic scintillator molecules are preferable.

  Examples of organic scintillator molecules include the following.

Benzoxazole derivatives : 1,1′-biphenyl 4-yl-6-phenyl-benzoxazole TLA, 2-phenylbenzoxazole, 2- (4′-methylphenyl) -benzoxazole, 2- (4′-methylphenyl) -5-methylbenzoxazole, 2- (4'-methylphenyl) -5-t-butylbenzoxazole, 2- (4'-t-butylphenyl) -benzoxazole, 2-phenyl-5-t-butyl- Benzoxazole, 2- (4′-t-butylphenyl) -5-t-butylbenzoxazole, 2- (4′-biphenylyl) -benzoxazole, 2- (4′-biphenylyl) -5-t-butylbenzo Oxazole, 2- (4′-biphenylyl) -6-phenyl-benzoxazole (PBBO), etc.
Oxazole derivatives : 2-p-biphenylyl-5-phenyloxazole (BPO), 2,2′-p-phenylenebis (5-phenyloxazole) (POPOB), 2,5-diphenyloxazole (PPO), 1,4- Bis [2- (5-phenyloxazolyl)] benzene (POPOP), 1,4-bis-2- (4-methyl-5-phenyloxazolyl) benzene (DMPOPOP), etc.
Oxadiazole derivatives : 2,5-diphenyloxadiazole (PPD), 2,5-diphenyl-1,3,4-oxadiazole, 2- (4′-t-butylphenyl) -5-phenyl-1 , 3,4-oxadiazole, 2,5-di- (4′-t-butylphenyl) -1,3,4-oxadiazole, 2-phenyl-5- (4 ″ -biphenylyl) -1 , 3,4-oxadiazole (PBD), 2- (4′-t-butylphenyl) -5- (4 ″ -biphenylyl) -1,3,4-oxadiazole (butyl-PBD), etc.
Terphenyl derivatives : 4,4 ″ -di-tert-amyl-p-terphenyl (DAT), etc.
Polynuclear aromatic compounds : 4,4′-bis (2,5-dimethylstyryl) diphenyl (BDB), p-terphenyl scintillator, etc.
Pyrazoline derivatives : 1-phenyl-3-mesityl-2-pyrazoline (PMP), 1,5-diphenyl-3- (4-phenyl-1,3-butadienyl) -2-pyrazoline (DBP), 1,5-diphenyl -Β-styrylpyrazoline (DSP), etc.
Phosphoramide derivatives : Anilinobis (1-aziridinyl) phosphine oxide (PDP), etc.
Thiophene derivatives : 2,5-bis-benzoxazolyl (2 ′)-thiophene, 2,5-bis- [5′-methylbenzoxazolyl (2 ′)]-thiophene, 2,5-bis- [ 4 ′, 5′-dimethylbenzoxazolyl (2 ′)]-thiophene, 2,5-bis- [4 ′, 5′-dimethylbenzoxazolyl (2 ′)]-3,4-dimethylthiophene, 2,5-bis- [5′-isopropylbenzoxazolyl (2 ′)]-3,4-dimethylthiophene, 2-benzoxazolyl (2 ′)-5- [7′-sec-butyl-benzo Oxazolyl (2 ′)]-thiophene, 2-benzoxazolyl (2 ′)-5- [5′-t-butyl-benzoxazolyl (2 ′)]-thiophene, 2,5-bis- [5′-t-butylbenzoxazolyl (2 ′)]-thiophene (BBOT) .

Examples of inorganic scintillator molecules include Ce-added Gd ₂ SiO ₅ , CsI, CsI (Tl), CsI (Na), Bi ₄ Ge ₃ O ₁₂ , Ce-added Lu ₂ SiO ₅ , NaI (Tl), CeF ₃ , PbWO _4. BaF ₂ , PbF ₂ , LiI (Eu) and the like.

  The scintillator molecules can be used in appropriate combination as long as radiation can be detected. As such a combination, for example, a combination of a first solute and a second solute used in a liquid scintillator can be employed. Examples of the first solute include p-terphenyl, 2,5-diphenyloxazole (PPO), 2- (4′-t-butylphenyl) -5- (4 ″ -biphenylyl) -1,3,4- And oxadiazole (butyl-PBD). Examples of the second solute include 1,4-bis [2- (5-phenyloxazolyl)] benzene (POPOP) and 1,4-bis-2- (4-methyl-5-phenyloxazolyl) benzene. (DMPOPOP) and the like. A preferable combination includes, for example, a combination of PPO and POPOP.

  The complex of the scintillator molecule is not particularly limited as long as it is a complex containing a scintillator molecule, and examples thereof include a complex composed of only a plurality of scintillator molecules, or a complex of a scintillator molecule and another substance. Among these, carrier particles containing a scintillator molecule are preferable.

  The carrier particles are not particularly limited as long as they can contain scintillator molecules, and examples thereof include silica nanoparticles. The average particle diameter of the silica nanoparticles is not particularly limited as long as it is a particle diameter obtained by a normal method for producing silica nanoparticles. The average particle diameter of the silica nanoparticles can be, for example, about 10 to 500 nm, preferably 30 to 400 nm, more preferably 70 to 300 nm, and still more preferably about 100 to 200 nm.

  “Contains” means that the scintillator molecule is attached on the surface of the carrier particle or contained within the carrier particle. The scintillator molecule is preferably contained within the carrier particle.

  A complex of scintillator molecules can be obtained according to a known method. For example, if it is an organic scintillator molecule containing silica nanoparticle, according to the method of patent document 1, a nonpatent literature 1, etc., it will obtain by forming a silica nanoparticle in presence of an organic scintillator molecule (for example, by sol-gel method). be able to. More specifically, the organic scintillator molecule-containing silica nanoparticles can be obtained by, for example, dissolving an organic scintillator molecule in an organic solvent and then adding a lower alcohol, a silicic acid source, and a catalyst thereto.

  Examples of the organic solvent for dissolving the organic scintillator molecule include DMSO, benzene, toluene, xylene, dioxane and the like. The compounding ratio of the organic scintillator and the organic solvent (organic scintillator weight: organic solvent weight) is not particularly limited as long as the organic scintillator can be dissolved in the organic solvent. The blending ratio can be, for example, about 1:10 to 90, preferably about 1:30 to 70.

  Compounds in which hydrogen atoms (preferably 1 to 3, more preferably 1 to 2) of benzene, such as benzoic acid, phenol and hydroquinone, are substituted with hydroxyl groups, carboxy groups, etc., when dissolving organic scintillator molecules By coexisting, the organic scintillator can be easily adapted to the silica nanoparticles. When these coexisting substances are added, the compounding ratio of the coexisting substances and the organic solvent can be, for example, about 1:10 to 90, preferably about 1:30 to 70.

  The lower alcohol is not particularly limited as long as it is a lower alcohol that can be used for forming silica nanoparticles by a sol-gel method. As a lower alcohol, methanol, ethanol, n-propanol, 2-propanol etc. are mentioned, for example, Preferably ethanol is mentioned. Although the compounding quantity of a lower alcohol is not specifically limited, For example, it can be about 1 to 5 times the organic solvent.

  The silicic acid source is not particularly limited as long as it is a silicic acid source that can be used for forming silica nanoparticles by a sol-gel method. Examples of the silicic acid source include alkoxysilanes, and more specifically, for example, tetraethyl orthosilicate (TEOS), tetramethyl orthosilicate (TMOS), etc., preferably tetraethyl orthosilicate. Although the compounding quantity of a silicic acid source is not specifically limited, For example, it can be about 1 / 500-1 / 5 of a lower alcohol.

  The catalyst is not particularly limited as long as it is a catalyst that can be used for forming silica nanoparticles by a sol-gel method. Examples of the catalyst include a base catalyst and an acid catalyst, and a base catalyst is preferable. Examples of the base catalyst include ammonia, and examples of the acid catalyst include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like.

  The ratio of the scintillator molecule to the total weight of the scintillator molecule complex is, for example, 5 to 80% by weight, preferably 15 to 70% by weight, more preferably 25 to 60% by weight, and further preferably 30 to 55% by weight. be able to.

  The scintillator may be a single type or a combination of two or more types.

  In the scintillator-immobilized silicate particles of the present invention, the scintillator is immobilized on the surface of the silicate particles. The scintillator may be directly immobilized on the surface of the silicate particles, or may be immobilized via another substance (for example, an adhesive). From the viewpoint that more scintillators can be fixed, it is preferable that the scintillator is fixed via an adhesive.

  The adhesive is not particularly limited as long as it is a substance that can adhere the scintillator to the silicate particles. Examples of the adhesive include an adhesive containing a silicon atom such as sodium silicate and tetraethyl orthosilicate, and preferably sodium silicate.

  The ratio of the scintillator in the total weight of the scintillator-immobilized silicate particles is, for example, 1 to 70% by weight, preferably 3 to 60% by weight, more preferably 5 to 50% by weight, and further preferably 10 to 50% by weight. be able to. Among these ranges, a preferable range when scintillator molecule-containing silica nanoparticles are used as the scintillator is, for example, 20 to 50% by weight, preferably 30 to 50% by weight.

  The scintillator-immobilized silicic acid particles can be obtained, for example, by mixing the silicic acid particles with an adhesive as necessary (first mixing) and then mixing with the scintillator (second mixing).

  The first mixing is preferably performed in the presence of a solvent. For example, when sodium silicate is used as an adhesive, it is preferable to perform the first mixing by mixing water glass, which is an aqueous solution, and silicate particles. Although the time of the 1st mixing is not specifically limited, For example, it can be about 6 to 48 hours. The mixing ratio of the silicate particles and the adhesive (silicate particle weight: adhesive weight) varies depending on the type of the adhesive, but when the adhesive is sodium silicate, for example, 1: 0.005. It can be -0.5, preferably 1: 0.01-0.1.

  The second mixing is also preferably performed in the presence of a solvent. It does not specifically limit as a solvent, For example, water, the organic solvent used for manufacture of the said scintillator molecule containing silica nanoparticle, a lower alcohol, etc. can be used. Although the time of 2nd mixing is not specifically limited, For example, it can be about 24 to 100 hours. The compounding ratio of silicic acid particles and scintillator (silicic acid particle weight: scintillator weight) varies depending on the type of scintillator, but is, for example, 1: 0.01 to 3, preferably 0.1 to 1.5. it can.

  After the second mixing, scintillator-immobilized silicate particles can be obtained by evaporating the solvent from the mixture as necessary.

2. Radiation detection material TECHNICAL FIELD This invention relates to the radiation detection material (it may be shown as "the radiation detection material of this invention" in this specification) containing the scintillator fixed silicic acid particle of this invention, and a binder. This will be described below.

  The binder is not particularly limited as long as it can adhere the scintillator-immobilized silicic acid particles of the present invention, and widely known binders can be used. Examples of the binder include an acrylic resin adhesive, an acrylic resin anaerobic adhesive, an acrylic resin emulsion adhesive, an α-olefin adhesive, a urethane resin adhesive, a urethane resin solvent adhesive, a urethane resin emulsion adhesive, and an ether. Cellulose, ethylene-vinyl acetate resin adhesive, epoxy resin adhesive, vinyl chloride resin solvent adhesive, vinyl acetate resin adhesive, phenol resin adhesive, polyamide resin adhesive, polyimide resin adhesive, chloroprene rubber Examples thereof include organic adhesives such as adhesives, silicone adhesives, styrene-butadiene rubber solution adhesives, nitrocellulose adhesives, polyvinyl alcohol adhesives, polyvinyl pyrrolidone resin adhesives, and melamine resin adhesives.

  The proportion of the scintillator-immobilized silicate particles of the present invention in the total weight of the radiation detection material of the present invention is not particularly limited as long as it is an amount capable of detecting radiation, but is, for example, 1 to 99% by weight, preferably It can be 10 to 95% by weight, more preferably 20 to 95% by weight, still more preferably 30 to 90% by weight, and still more preferably 60 to 90% by weight.

The radiation detection material of the present invention may contain a substance that enhances fluorescence emitted from the scintillator (sometimes referred to as “fluorescence enhancing substance” in this specification). The fluorescence derived from the scintillator can be enhanced by the fluorescence enhancing substance, whereby the radiation detection sensitivity can be further increased. Examples of the fluorescence enhancing substance include substances that cause surface plasmon resonance by light of a specific wavelength (gold nanoparticles, silver nanoparticles, etc.). When gold nanoparticles or silver nanoparticles are used, the particle size can be appropriately set according to the wavelength of fluorescence emitted from the scintillator molecules. Suitable combinations include a combination of scintillator molecules: PPO and POPOP and a fluorescence enhancing substance: gold nanoparticles. In the case of the combination, a substance (for example, O-Auramin or the like) for converting fluorescence emitted from POPOP into fluorescence having a wavelength that is more easily absorbed by the gold nanoparticle according to the particle diameter of the gold nanoparticle. It is desirable to include in the radiation detection material. This combination is particularly suitable for increasing the detection sensitivity of radiation emitted from ⁸⁹ Sr, ²⁰⁴ Tl and the like.

  The radiation detection material of the present invention may contain other components as long as radiation detection is possible. Examples of other components include silica nanocapsules and porous silica nanoparticles, surface-modified silica nanoparticles and porous silica nanoparticles.

  The shape of the radiation detection material of the present invention is not particularly limited, and may be various shapes such as a sheet shape, a spherical shape, a column shape, a rectangular parallelepiped shape, etc., depending on the shape of the detection target. From the viewpoint that two-dimensional imaging of radiation dose is easier to perform, a sheet shape is preferable. The thickness of the sheet can be, for example, about 0.01 mm to 5 mm, preferably about 0.01 mm to 2 mm.

  The radiation detection material of the present invention can be obtained by mixing the scintillator-immobilized silicate particles of the present invention, a binder, and, if necessary, a fluorescence enhancing substance and other components. For example, it can be obtained by mixing the above components in the presence of a suitable solvent such as water or alcohol and then removing the solvent by drying or the like. Moreover, you may shape | mold so that it may become a desired shape before drying or after drying.

The radiation detection material of the present invention can detect radiation emitted from various nuclides such as ³ H, ⁶³ Ni, ¹⁴ C, ³⁵ S, ³³ P, ⁸⁹ Sr, ²⁰⁴ Tl, ³² P, and ²⁴¹ Am. . The radiation detection material of the present invention is preferably used for detection of radiation of 100 to 500 keV, more preferably 150 to 300 keV (for example, radiation emitted from ³⁵ S, ³³ P, etc.) from the viewpoint that higher detection sensitivity can be obtained. Is suitable. On the other hand, the radiation detection material of the present invention is preferably a radiation emitted from ³⁵ S, ³³ P, or ³² P, more preferably ³² , from the viewpoint that a higher detection sensitivity can be obtained compared to the case where the scintillator is used alone. It is particularly suitable for detecting radiation emitted from P.

  EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

Test Example 1: Evaluation of radiation detection sensitivity of scintillator-immobilized silicate particles Scintillator-immobilized silicate particles were prepared, and the radiation detection sensitivity was measured and evaluated. Specifically, it was performed as follows.

  Silica powder (manufactured by Hiroura Mining Co., Ltd., silicon dioxide purity 99.8%) (2.2680 g of silica powder with a particle size of 2.25 μm, 2.130 g of silica powder with a particle size of 4.77 μm, silica powder 2 with a particle size of 6.78 μm) 1436 g, or 2.1291 g of silica powder having a particle diameter of 10 μm) was added to 25 mL of a 0.54 wt% aqueous water glass solution and stirred at room temperature for 1 day. On the other hand, 30 mL of dimethyl sulfoxide (DMSO), 1,4-bis- [2- (5-phenyloxazolyl)] benzene (POPOP) 52.9-55.1 mg, 2,5-diphenyloxazole (PPO) After dissolving 524.3 to 544.2 mg and 512.8 to 611.1 mg of benzoic acid, 70 mL of ethanol, 2.5 mL of tetraethyl orthosilicate (TEOS), and 2.5 mL of concentrated aqueous ammonia were added and stirred. As disclosed in Non-Patent Document 1, this operation forms scintillator molecule-containing silica nanoparticles having a particle size of about 100 to 200 nm. The solution containing the scintillator molecule-containing silica nanoparticles was added to the above mixed solution of silica powder and water glass aqueous solution and stirred at room temperature for about 3 days. Thereafter, a solvent such as ethanol was evaporated while heating to about 120 to 140 ° C. with a heater to obtain powder (scintillator-immobilized silicic acid particles).

  Further, a powder (scintillator (scintillator molecule-containing silica nanoparticles)) was obtained in the same manner except that the silica powder was not added.

  The total weight of the obtained powder (A), the weight of the scintillator molecule-containing silica nanoparticles in the total weight (= total weight-silica powder weight) (B), and the ratio of the weight of the scintillator molecule-containing silica nanoparticles to the total weight (B / A) is shown in Table 1.

  1 mL of 1% PVA (polymerization degree 500) aqueous solution was added to 50 mg of the obtained powder (scintillator-immobilized silicic acid particles or scintillator (scintillator molecule-containing silica nanoparticles)), and mixed in an agate mortar. The obtained mixed solution was applied onto a 3 cm × 3 cm transparent plastic plate and dried at room temperature while rotating with a shaker to obtain a sheet-like radiation detection material.

In the obtained sheet-like radiation detection material, a solution containing a radioisotope ( ³ H (37 kBq, 1 μL), ⁶³ Ni (37 kBq, 10 μL), ¹⁴ C (740 Bq, 1 μL), ³⁵ S (29 kBq, 0.1 μL) , ³³ P (16.2 kBq, 0.1 μL), ⁸⁹ Sr (37 kBq, 10 μL), or ³² P (8.6 kBq, 0.1 μL)) ( ³ H, ¹⁴ C, ³⁵ S, ³³ P, and ³² P Was made by Perkin Elmer, ⁸⁹ Sr and ⁶³ Ni were made by Eckert & Ziegler Isotope Products (EZIP). The sheet-like radiation detection material was set in the second stage of Imager (ImageQuant LAS-4000 Mini, manufactured by GE Healthcare Life Sciences), and a fluorescence image of the sheet was obtained with Precision 5 min. An example of the obtained fluorescence image (when scintillator-immobilized silicate particles are used) is shown in FIG. During the ^image, since the area of the black areas of the position dropwise (37 kBq) containing ³ H was about 10 mm ^2, in the case ^{where 3} H of 3.7kBq are present in 1 mm ^2, the scintillator It was shown that detection was possible with a sheet-like radiation detection material using immobilized silicate particles.

In the fluorescent image, the intensity (= fluorescence intensity) of the fluorescent region (black region) was quantified. Further, the corrected fluorescence intensity was obtained by multiplying the numerical value of this fluorescence intensity by the reciprocal (A / B) of the ratio (B / A) of the weight of the scintillator molecule-containing silica nanoparticles to the total weight of the powder. The corrected fluorescence intensity is adjusted so that the scintillator having the same weight as the scintillator weight (50 mg) in the sheet-shaped radiation detection material without the silica powder (B / A = 1) is included in the sheet-shaped radiation detection material. The fluorescence intensity is shown. If this corrected fluorescence intensity is higher than that without the silica powder, it means that the radiation detection sensitivity per scintillator of a constant weight is further increased. ³ H results are shown in Table 2, ⁶³ Ni results in Table 3, ¹⁴ C results in Table 4, ³⁵ S results in Table 5, ³³ P results in Table 6, and ⁸⁹ Sr results. The results for Table 7 or ³² P are shown in Table 8.

As shown in Tables 2 to 8, when the scintillator-immobilized silicate particles are used (when the silica powder is present), the correction is better than when the scintillator is used alone (when the silica powder is not present). The fluorescence intensity (that is, the radiation detection sensitivity per scintillator of a constant weight) was about twice or more higher. Among these, ³⁵ S, ⁸⁹ Sr, and ³² P were 5 times or more (especially 20 times or more for ³² P), although depending on the particle size of the silica powder. As mentioned above, it was shown that the radiation detection sensitivity per fixed weight scintillator improves by fixing a scintillator to a silicic acid particle.

From Tables 2 to 8, the fluorescence intensity obtained by the detection of ³⁵ S (radiation energy: 167 keV) and ³³ P (radiation energy: 249 keV) is compared with the fluorescence intensity obtained by other various detections. It was high.

Test Example 2: Evaluation of influence of fluorescence enhancing substance on radiation detection sensitivity The influence of the substance (fluorescence enhancing substance) that enhances the fluorescence emitted from the scintillator on the radiation detection sensitivity was evaluated. Specifically, it was performed as follows.

  To 50 mg of the powder (scintillator-immobilized silicic acid particles or scintillator (scintillator molecule-containing silica nanoparticles)) obtained in Test Example 1, 20 mL of 1% PVA (polymerization degree 500) aqueous solution, gold fine particles (fluorescence enhancement substance) 1.8 mL of 0.0070% by weight aqueous dispersion (particle size 15 nm) (Tanaka Kikinzoku Kogyo Co., Ltd., Au colloid solution-SC) and 2 mg of O-Auramin were added and mixed in an agate mortar. The obtained mixed solution was applied onto a 3 cm × 3 cm transparent plastic plate and dried at room temperature while rotating with a shaker to obtain a sheet-like radiation detection material.

A solution ( ⁸⁹ Sr (3.7 kBq, 1 μL) or ²⁰⁴ Tl (3.7 kBq, 1 μL)) containing a radioisotope was dropped into the obtained sheet-shaped radiation detection material (including a fluorescence enhancing substance). Furthermore, a solution containing a radioactive isotope ( ⁸⁹ Sr (37 kBq, 10 μL) or ²⁰⁴ Tl (37 kBq, 10 μL)) was dropped onto the sheet-like radiation detection material (not including the fluorescence enhancing substance) obtained in Test Example 1. . In the same manner as in Test Example 1, a fluorescence image was obtained and the fluorescence intensity was digitized. The amount of RI dropped on the sheet-like radiation detection material containing the fluorescence enhancement material was 1/10 of the amount of RI dropped on the sheet-like radiation detection material containing no fluorescence enhancement material. The fluorescence intensity obtained from the detection material was multiplied by 10 and compared with the fluorescence intensity obtained from the sheet-like radiation detection material containing no fluorescence enhancing substance. The results of ⁸⁹ Sr are shown in Table 9, and the results of ²⁰⁴ Tl are shown in Table 10.

  From Tables 9 to 10, it was shown that the radiation detection sensitivity of the sheet-form radiation detection material can be increased by a factor of 2 or more by including a fluorescence enhancing substance.

Claims (5)

Containing silica particles and immobilized on the surface of the particles the scintillator,
The silica particles have an average particle size of 1.5 to 20 μm,
The scintillator is silica nanoparticles containing organic scintillator molecules, and
The silica nanoparticles have an average particle size of 30 to 400 nm,
Scintillator-immobilized silicate particles. The scintillator-immobilized silicic acid particle according to claim 1 , wherein the scintillator is immobilized on the silica particle through an adhesive. A radiation detection material comprising the scintillator-immobilized silicate particles according to claim 1 or 2 and a binder. The radiation detection material according to claim 3 , which is in a sheet form. The radiation detection material of Claim 3 or 4 containing the substance which enhances the fluorescence emitted from a scintillator.