TY - JOUR
AU1 - Miyoshi,, Hirokazu
AU2 - Hiroura,, Mitsunori
AU3 - Tsujimoto,, Kazunori
AU4 - Irikura,, Namiko
AU5 - Otani,, Tamaki
AU6 - Shinohara,, Yasuo
AB - Abstract A new scintillation imaging material [scintillator–silica fine powder (FP)] was prepared using silica FPs and scintillator–encapsulating silica nanoparticles (NPs) (scintillator–silica NPs). The wt% values of scintillator–silica NPs on the scintillator–silica FPs were 38, 43, 36 and 44%. Scintillation images of 3H, 63Ni, 35S, 33P, 204Tl, 89Sr and 32P dropped on the scintillator–silica FPs were obtained at about 37 kBq per 0.1–10 µl with a charge-coupled device (CCD) imager for a 5 min exposure. In particular, high-intensity CCD images of 35S were selectively obtained using the 2.25, 4.77 and 10 µm silica FPs with scintillator–silica NPs owing to the residual S of dimethyl sulfoxide in the preparation. Scintillation images of 3H at 1670 ± 9 Bq/0.5 µl and 347 ± 6 Bq/0.5 µl dropped in a 2 mm hole on the scintillator–silica FPs (6.78 and 10 µm) were also obtained using the CCD imager for a 2 h exposure. INTRODUCTION To date, liquid scintillators such as 2,5-diphenyloxazole (PPO) and 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP) have been used to determine the radioactivities of beta-particles precisely and effectively. However, they are composed of several organic phosphors dissolved in some organic solvents such as benzene and toluene. Therefore, some materials prepared without using organic solvents or using a mixture of organic phosphors were proposed, for example, polystyrene beads containing some organic phosphors with a surfactant dispersed in water(1) to detect alpha- and beta-particles, and a plastic scintillator sheet to detect beta-particles, efficiently(2). There are many publications that describe plastic scintillators(3). For example, the sensitivity of 1.2 Bq/cm2 for tritium was calculated using the detection efficiency of tritium and not the actual measurement of 1.2 Bq/cm2 for tritium(4). Recently, the plastic scintillator(5) and its sheet(6) to detect 3H quantitatively and precisely have proposed. Moreover, several organic phosphors encapsulated in silica nanoparticles (NPs) (scintillator–silica NPs)(7) have been reported. Scintillator–silica NPs are prepared by a sol-gel method(8), and an aqueous suspension of scintillator–silica NPs is dropped on a wipe paper to coat the surface of the paper. The scintillator–silica NPs-coated wipe paper was used to successfully detect 3H contaminating a dried acryl plate without the liquid scintillator. However, the dropped 3H-contaminated water is absorbed by the paper deeply and 3H is not completely captured by the photomultiplier tube (PMT) on the paper. Some mechanism is required to capture 3H completely using other materials such as scintillator–silica NPs. Therefore, we proposed scintillator–silica NPs on a silica fine powder (FP) and attempted to form the powder into a sheet for detecting 3H rapidly as a contaminant by imaging using a commercial charge-coupled device (CCD) imager. Usually, radiation is imaged using an imaging plate (IP, Fuji Film Co., Ltd.) or a solid scintillator sheet (Biospace Lab.). First, a radioisotope (RI) is applied onto the IP and its radiation of beta-particles or gamma-rays, for example, emits energy to the IP. The emitted energy is stored in the stimulable phosphor of the IP. When laser light excites the energy stored in the stimulable phosphor, the light emitted is detected by a PMT. Then, the intensity of each phosphor forms an image on a personal computer. The stored radiation energy decays with time and is erased with white light. A special IP for 3H (BAS-TR), which has no protective layer, is used and is contaminated by a 3H-labeled compound. 3H, which has a quite low beta-particle energy (18.6 keV)(9), must come in contact with the surface of the IP. Using 0.76 mg/cm2 surface density for 18.6 keV of beta-particles, a maximum range of 3.3 µm in SiO2 (2.3 g/cm3) was calculated(10). Therefore, the IP, which is expensive, cannot be used repeatedly (Fuji film Co., LTD., TR2040, 20 × 40 cm2 ~$800/sheet ($9 for 3 × 3 cm2)). On the other hand, a solid scintillator sheet for MicroIMAGER™ (GE Healthcare Co., Ltd) emits light when an RI comes in contact with it and the radiation energy generated is not stored. The sheet being very thin requires careful handling to prevent its breakage. It is also expensive (11 × 11 cm2, ~$700/sheet ($52/3 × 3 cm2)) particularly for 3H imaging because of 3H contamination caused by the required direct contact, as mentioned above. On the other hand, a plastic scintillator sheet is also expensive (Saint-Gobain Crystals, BC-400, thickness 1 mm, 38 × 38 cm2, $1200/sheet ($7.5/3 × 3 cm2)) and cannot absorb a liquid contaminant because of its hydrophobic surface. In this study, a new scintillation imaging material was prepared using scintillator–silica Nps and silica FP at a low-cost (~$2.3/g, 13 × 13 cm2/g as 0.11$(11) for 3 × 3 cm2/0.05 g) with negligible amount of carbon, which is favorable for green chemistry. That is, no organic solvents such as benzene or toluene in a liquid scintillator, no polymer in a plastic scintillator, and no surfactant in an aqueous sample prepared using a liquid scintillator were used. The proposed use of scintillator–silica FPs is to visualize a scintillation image using a commercial CCD imager after absorbing a beta-particle emitter aqueous liquid on the hydrophilic surface. FP was used as a support to capture 3H completely. The detection sensitivity as an image was determined on the basis of the successful imaging of 3H beta-particles using a commercial CCD imager. The CCD imager has been widely used in the life science area and the scintillation images obtained using this imager are easier to observe than those obtained using PMT. Furthermore, selective detection of 3H, 63Ni, 35S, 33P, 204Tl, 89Sr and 32P and its mechanism were also examined using scintillation images of these radioactive elements. This material is proposed for imaging a tritium contaminant directly and easily. EXPERIMENTAL METHODS Chemicals PPO and sodium silicate solution (~14% NaOH, ~27% SiO2) were purchased from Sigma-Aldrich Co., Ltd. POPOP, ethyl alcohol, concentrated ammonia solution (28%), tetraethyl orthosilicate (TEOS), dimethylsufoxide (DMSO), polyvinyl alcohol (PVA) (n = 500) and benzoic acid were purchased from Wako Pure Chemicals Co., Ltd. These chemicals were of reagent grade and were used without purification. Silica FPs (2.25, 4.77, 6.78 and 10 µm) used in this study were prepared by Hiromura Kogyo Co., Ltd. Their particle sizes were measured using a particle size analyzer, CILAS 920 (Cilas Co., Ltd.). Aerosil (Aerosil 200) of 20 nm size was purchased from Japan Aerosil Co., Ltd. Distilled water prepared using a RO system was used throughout the experiments (EASYpure RoDi, Thermo Scientific Co., Ltd.). 3H at 9.25 MBq/25 µl [adenosine 5′-triphosphate (ATP) tetrasodium, salt, (2,8–3H)-], 14C at 1.85 MBq/25 µl [adenosine 5′-diphosphate (ADP) trisodium salt, (8–14C)], 35S at 18.5 MBq/49 µl [methionine l-(35S)-], 33P at 3.7MBq/10 µl [ATP, (γ-33P)-] and 32P at 9.25 MBq /25 µl [ATP, (γ-32P)-] were prepared by PerkinElmer Co., Ltd. 89Sr at 3.7 MBq/ml, 63Ni at 3.7 MBq/ml and 204Tl at 3.7 MBq/ml in 40% hydrochloric aqueous solution (Eckert & Ziegler Isotope Products) were purchased from Japan Radioisotope Association. Their RIs were used in a controlled area of Radioisotope Research Center. Preparation of Scintillator–Silica FPs and their Sheets Silica FPs (2.25, 4.77, 6.78 and 10 µm) were used to fix scintillator–encapsulating silica nanoparticles (scintillato–silica NPs). As reference materials, scintillator–silica NPs mixed with Aerosil powder and only scintillator–silica NPs were used. An organic scintillator composed of PPO, POPOP and benzoic acid was used, the preparation of which is illustrated in Figure 1. Figure 1. Open in new tabDownload slide Preparation scheme for scintillator–silica FPs and scintillator-silica NP. Figure 1. Open in new tabDownload slide Preparation scheme for scintillator–silica FPs and scintillator-silica NP. First, ~2.1 g of 4.77, 6.78 or 10 µm silica FP or 2.3 g of 2.25 µm silica FP was mixed with 25 ml of 0.54 wt% sodium silicate solution [50 ml of sodium silicate solution was used for Aerosil (2.2 g)]. The mixtures were allowed to stand for 1 d at room temperature. A reference material was prepared without silica FP as described above [hereafter referred to as only scintillator–silica NPs]. After 52.9 to 55.1 mg of POPOP, 524.3 to 544.2 mg of PPO and 512.8 to 611.1 mg of benzoic acid were dissolved in a 30 ml of DMSO, 70 ml of ethyl alcohol, 2.5 ml of TEOS and 2.5 ml of concentrated ammonia solution were poured into the organic scintillator-containing DMSO, and the resulting solution was stirred at room temperature. This solution was mixed with silica FP dispersed in sodium silicate solution and stirred for 3 d at room temperature. Then, the solution was evaporated by heating using a hot stirrer at ~373 K to obtain scintillator–silica FP. Finally, ~1.6 g of only scintillator–silica NPs, 4.1 g of Aerosil, and 3.7, 3.7, 3.3 and 3.8 g of 2.25, 4.77, 6.78 and 10 µm scintillator–silica FPs, respectively, were obtained as shown in Table 1. Scintillator–silica NPs were examined by scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS) using JSM-6510 and 6510 (LA), respectively. Table 1. Contents of scintillator–silica NPs and silica FPs. . Scintillator–silica FPs (g) . Silica FPs/g . Scintillator–silica NPs (%) . Nonea 1.6 0 100 Aerosil 1.9 2.2 46 2.25 µm FP 1.4 2.3 38 4.77 µm FP 1.6 2.1 43 6.78 µm FP 1.2 2.1 36 10 µm FP 1.7 2.1 44 . Scintillator–silica FPs (g) . Silica FPs/g . Scintillator–silica NPs (%) . Nonea 1.6 0 100 Aerosil 1.9 2.2 46 2.25 µm FP 1.4 2.3 38 4.77 µm FP 1.6 2.1 43 6.78 µm FP 1.2 2.1 36 10 µm FP 1.7 2.1 44 aOnly scintillator–silica NPs. Table 1. Contents of scintillator–silica NPs and silica FPs. . Scintillator–silica FPs (g) . Silica FPs/g . Scintillator–silica NPs (%) . Nonea 1.6 0 100 Aerosil 1.9 2.2 46 2.25 µm FP 1.4 2.3 38 4.77 µm FP 1.6 2.1 43 6.78 µm FP 1.2 2.1 36 10 µm FP 1.7 2.1 44 . Scintillator–silica FPs (g) . Silica FPs/g . Scintillator–silica NPs (%) . Nonea 1.6 0 100 Aerosil 1.9 2.2 46 2.25 µm FP 1.4 2.3 38 4.77 µm FP 1.6 2.1 43 6.78 µm FP 1.2 2.1 36 10 µm FP 1.7 2.1 44 aOnly scintillator–silica NPs. Approximately 25 mg or 50 mg of each scintillator–silica FP (only scintillator–silica NPs, Aerosil, and 2.25, 4.77, 6.78 and 10 µm silica FPs) was mixed with 0.5 or 1 ml of 1% PVA aqueous solution in agate mortar and pestle. First, this 50 mg/ml dispersion was dropped and coated on a 3 × 3 cm2 transparent plastic plate (thickness: 0.4 mm) on a minishaker (SL3D, SeouLin Bioscience Co., Ltd.). Then, the plate was dried at room temperature and the thus prepared scintillator–silica FP-PVA-coated plastic plate was used for detection of beta-particle emitters, as shown in Figure 1S. Second, to obtain the same area with the dropped RI solution on the scintillator–silica FP, seven holes of 2, 2.5, 3, 3.5, 4, 4.5 and 5 mm diameter were prepared per line on a 6 × 8 cm2 acryl plate (thickness: 5 mm), as shown in Figure 2S. About 10 µl of 25 mg/0.5 ml scintillator–silica FP dispersion was dropped on 2 and 2.5 mm holes and 20 µl was dropped on 3, 3.5, 4, 4.5 and 5 mm holes. Detection of Beta-Particles of RIs with Scintillator–Silica FP Beta-particle emitters, namely, 3H [Eβmax. = 18.6 keV], 63Ni [Eβmax. = 66.9 keV], 14C [Eβmax. = 157 keV], 35S [Eβmax. = 167 keV], 33P [Eβmax. = 249 keV], 204Tl [Eβmax. = 764 keV], 89Sr [Eβmax. = 1.495 MeV] and 32P [Eβmax. = 1.71 MeV], were dropped on the scintillator–silica FPs [1, only scintillator–silica NPs; 2, Aerosil; and 3, 2.25 µm FP; 4, 4.77 µm FP; 5, 6.78 µm; 6, 10 µm FPs, which were coated with 50 mg/ml scintillator–silica FPs dispersed in 1 wt% PVA aqueous solution on a 3 × 3 cm2 plastic plate (thickness, 0.4 mm)]. The radioactivities of the RIs dropped on the plate were 37 kBq of 3H (1 µl), 37 kBq of 63Ni (10 µl), 740 Bq of 14C (1 µl), 37 kBq of 35S (0.1 µl), 37 kBq of 33P (0.1 µl), 37 kBq of 204Tl (10 µl), 37 kBq of 89Sr (10 µl) and 37 kBq of 32P (0. 1 µl). A 3H aliquot of 37, 1.7, or 0.35 kBq was dropped on the acryl plates with 2, 2.5, 3, 3.5, 4, 4.5 and 5 mm holes to investigate the sensitivity of the plates to 3H beta-particles. All the obtained scintillation and CCD images were digitized using a LAS-4000mini Imager (General Electric Co., Ltd., GE HealthCare Life Sciences: chemiluminescence mode; exposure type; precision mode; exposure times, 5 min and 2 h for the sensitivity experiment; sensitivity/resolution, standard). RESULTS AND DISCUSSION Scintillator–silica NPs were ~9 nm in size, as shown in Figure 3S. The absorption spectrum of the scintillator–silica NPs dispersed in ethyl alcohol is shown in Figure 4S, which indicates a mixture of PPO (~303 nm), POPOP (~360 nm) and benzoic acid (~260 nm)(12). It indicates that these three compounds are contained in the scintillator–silica Nps. Figure 5S shows the excitation and emission spectra of the scintillator–silica NPs obtained using an RF-5300PC fluorescence spectrometer. As shown in Figure 5S, the peaks in the figure corresponded to the excitation and emission peak wavelengths of POPOP. The shoulder wavelength at ~300 nm in Figure 5S corresponded to the absorption peak of PPO. Figure 2 shows SEM images of scintillator–silica FPs [(a) only scintillator–silica NPs, (b) about 20 nm NPs, (c) 2.25 µm, (d) 4.77 µm, (e) 6.78 µm and (f) 10 µm FPs]. As shown in Figure 2, ~1.2 to 6 µm aggregations composed of small particles were observed in only scintillator–silica NPs (a) and Aerosil (b) SEM images. Figure 2. Open in new tabDownload slide SEM images of scintillator–silica FPs. (a) Only scintillator–silica NPs, (b) Aerosil, (c) 2.25, (d) 4.77, (e) 6.78 and (f) 10 µm FPs. Scale bar indicates 5 µm. Figure 2. Open in new tabDownload slide SEM images of scintillator–silica FPs. (a) Only scintillator–silica NPs, (b) Aerosil, (c) 2.25, (d) 4.77, (e) 6.78 and (f) 10 µm FPs. Scale bar indicates 5 µm. In the images shown in (c), (d), (e) and (f), some solid fractions were observed and they increased in size, as shown from (c) to (f). These images indicate that scintillator–silica NPs were adsorbed on the scintillator–silica FPs and their sizes [(c) 1.4–3.7 µm, (d) 1.3–4.5 µm, (e) 2.2–8.6 µm, (f) ~13 µm] were close to those of silica FPs (2.25, 4.77, 6.78 and 10 µm, respectively). The silica FP sizes may change owing to the adsorption of scintillator–silica NPs, a silicate, or a small fraction of silica FPs during preparation. Detection of Beta-Particle Emitters by Scintillator–Silica FPs Typical CCD images and the digitized images of 3H, 14C, 35S, 33P and 32P RIs on the plate coated with only scintillator–silica NPs, Aerosil, or 2.25 µm, 4.77 µm, 6.78 µm or 10 µm scintillator–silica FP obtained using LAS-4000mini are shown in Figure 3b. Figure 3a shows a configuration of scintillator–silica FPs and RIs on each plate. The radioactivities of all RIs dropped on the plate were 37 kBq for 3H, 63Ni, 35S, 33P, 204Tl, 89Sr and 32P, and 740 Bq for 14C. Except for 14C, these RIs were clearly observed using the CCD imager. Figure 3. Open in new tabDownload slide (a) Example of position of each dropped RI and the position of each plate. 1, only scintillator–silica NPs; 2, Aerosil; 3, 2.25; 4, 4.77; 5, 6.78; and 6, 10 µm FPs. (b) Digitized (left) and CCD images (right) oriented as in (a). Figure 3. Open in new tabDownload slide (a) Example of position of each dropped RI and the position of each plate. 1, only scintillator–silica NPs; 2, Aerosil; 3, 2.25; 4, 4.77; 5, 6.78; and 6, 10 µm FPs. (b) Digitized (left) and CCD images (right) oriented as in (a). Figure 4 shows the relationship between the corrected intensity and the size of scintillator–silica FPs [only scintillator–silica NPs, Aerosil, and 2.25, 4.77, 6.78 and 10 µm FPs]. The corrected intensity is obtained using the following equation. Figure 4. Open in new tabDownload slide Plots of corrected intensity against eight types of beta-particle emitter for scintillator–silica FPs [only scintillator–silica NPs (none); Aerosil; and 2.25, 4.77, 6.78 and 10 µm FPs]. Corrected intensity = mean intensity deteremined by ImageJ software × area ÷ wt% of scintillator–silica FPs. Figure 4. Open in new tabDownload slide Plots of corrected intensity against eight types of beta-particle emitter for scintillator–silica FPs [only scintillator–silica NPs (none); Aerosil; and 2.25, 4.77, 6.78 and 10 µm FPs]. Corrected intensity = mean intensity deteremined by ImageJ software × area ÷ wt% of scintillator–silica FPs. Comparing between the results of silica FPs and only scintillator–silica NPs, the corrected intensity of the CCD images was high. In particular, the sensitivities to 35S and 33P were high specifically to 4.77, 6.78 and 10 µm scintillator–silica FPs. These findings indicate that the silica FPs effectively captured 35S and 33P on their surfaces near scintillator–silica NPs, as shown in Figure 5. Figure 5. Open in new tabDownload slide Scheme of concentration effect of beta-particle emitter on surface of silica FPs for efficient beta-particle detection. Figure 5. Open in new tabDownload slide Scheme of concentration effect of beta-particle emitter on surface of silica FPs for efficient beta-particle detection. Figure 6 shows the beta-particle energy dependence of the corrected intensity of CCD images obtained using scintillator–silica FPs, as determined from data shown in Figure 4. The beta-particle maximum energies of all the RIs were 18.6 keV for 3H, 66.9 keV for 63Ni, 157 keV for 14C, 167 keV for 35S, 249 keV for 33P, 764 keV for 204Tl, 1495 keV for 89Sr and 1710 keV for 32P. The radioactivities of all RIs were all 37 kBq except for 14C, which was 740 Bq. It was found that the detection of 35S was enhanced for Aerosil, and 2.25, 4.77, 6.78 and 10 µm scintillator–silica FPs. This may be due to the remaining sulfur on the scintillator–silica FPs, because DMSO was used in the preparation. Figure 6. Open in new tabDownload slide Plots of corrected intensity vs. beta-particle energy for scintillator–silica NP and scintillator–silica FPs [only scintillator–silica NPs (none); Aerosil; and 2.25, 4.77, 6.78 and 10 µm FPs]. Figure 6. Open in new tabDownload slide Plots of corrected intensity vs. beta-particle energy for scintillator–silica NP and scintillator–silica FPs [only scintillator–silica NPs (none); Aerosil; and 2.25, 4.77, 6.78 and 10 µm FPs]. These scintillator–silica FPs may have a large amount of remaining sulfur. EDS analysis of scintillator–silica FPs indicated that a small amount of sulfur existed on the surface of the scintillator–silica FPs. The S atom was observed on the surface of the scintillator–silica FPs at 5 kV (shallow, 0.09 ± 1.19 wt%), 10 kV (middle, 0.04 ± 0.55 wt%) and 15 kV (deep, not detected) of accelerated voltage. These findings indicate that the remaining S distributed on the surface of the scintillator–silica FPs. On the other hand, 204Tl was detected at the lowest amount except in the sample without silica FPs (None), suggesting that such a heavy isotope may penetrate into silica FPs and its emission light may not be sufficient to reach the outer surface. Finally, by comparing these results with those of only scintillator–silica NPs, we found that these scintillator–silica FPs showed high sensitivity to 35S, indicating the supportive effect (isotope exchange reaction) of the remaining S for the capture of 35S by silica FPs and Aerosil, as shown in Figure 6. In particular, the 4.77, 6.78 and 10 µm silica FPs enhanced beta-particle-induced scintillation images. Detection of Lower than 3.7 kBq of 3H on Scintillation Images Obtained Using CCD Imager Figure 7a and b shows digitized and CCD images of 1670 ± 8 and 347 ± 6 Bq of 3H dropped in the holes of 2, 4 and 5 mm diameters on the acryl plate. Measurement conditions were as follows: chemiluminescence mode; exposure type, precision mode; exposure time, 2 h. Radioactivities were precisely determined using a glass vial containing 5 ml of a liquid scintillator (Ecoschint™ XR, National Diagnostics) and a liquid scintillation counter (LSC-6100, Hitachi Aloka Medical, Ltd.). It was found that even 347 Bq of 3H was observed as a scintillation image for a 2 h exposure and can be measured repeatedly. In the case of IP at 30 min exposure, ~400 to 500 Bq was detected using FLA-9000 with PMT and cannot be measured repeatedly (data not shown). Figure 7. Open in new tabDownload slide (a) Digitized image of acryl plate with 2 and 4 mm holes (left: two images) and CCD image after dropping 3H of ~1670 ± 8 and 347 ± 6 Bq in the holes (right images). (b) Digitized and CCD images of acryl plate with 5 mm holes. Figure 7. Open in new tabDownload slide (a) Digitized image of acryl plate with 2 and 4 mm holes (left: two images) and CCD image after dropping 3H of ~1670 ± 8 and 347 ± 6 Bq in the holes (right images). (b) Digitized and CCD images of acryl plate with 5 mm holes. The coating content of scintillator–silica FP per area of a hole increased with decreasing hole diameter from 5 to 2 mm except for the hole diameter of 3 mm, as shown in Figure 8a, because the coating volume is the same. The intensity per area of the CCD image also increased, and 6.78 and 10 µm silica FPs on the scintillator–silica FPs showed the maximum intensity per area, as shown in Figure 8b, indicating that the enhancement of the 3H image is due to the content of the scintillator–silica FPs and the silica FPs, which promote the capture of 3H. Finally, the increase in the content of the scintillator–silica FPs per unit area led to the effective capture of 3H beta-particles. Figure 8. Open in new tabDownload slide (a) Relationship between content of scintillator–silica FPs in each hole in the plate and diameter of the hole. (b) Relationship between intensity and area for 1670 ± 8 Bq. Only scintillator–silica NPs (open circle), Aerosil (open square), and 2.25 µm (open triangle), 4.77 µm (solid circle), 6.78 µm (solid triangle) and 10 µm (solid square) FPs. Figure 8. Open in new tabDownload slide (a) Relationship between content of scintillator–silica FPs in each hole in the plate and diameter of the hole. (b) Relationship between intensity and area for 1670 ± 8 Bq. Only scintillator–silica NPs (open circle), Aerosil (open square), and 2.25 µm (open triangle), 4.77 µm (solid circle), 6.78 µm (solid triangle) and 10 µm (solid square) FPs. CONCLUSIONS Silica FPs played an important role in the accumulation of 3H and scintillator–silica NPs on the surface of silica FPs. They captured a sufficient amount of 3H for imaging, which was detected by the scintillator–silica NPs. About 347 ± 6 Bq of 3H could be detected only when using 2-mm-diameter scintillator–silica FPs on a CCD image. This new scintillation material was stable (thus, easy to handle) and low-cost with a small negligible amount of carbon (which is favorable for green chemistry). The 3H-contaminated scintillator–silica FPs as radioactive waste were easily confined in a dissolved silica glass. SUPPLEMENTARY MATERIAL Supplementary material can be found at RADIATION PROTECTION DOSIMETRY online. ACKNOWLEDGEMENTS We are very grateful to Mr. Tomoyuki Ueki of Tokushima University, Institute of Technology and Science Center for technical support in the analyses using electron microscopy techniques (Grade 2), SEM observations, and EDS analysis of scintillator–silica NPs and scintillator–silica FPs. FUNDING This work was supported by SME support initiatives by small/micro enterprises to develop or produce unique new products, introduce new sales methods or provide new services (JAPAN) through Grant Number 2536110038. REFERENCES 1 Zhu , D. and Jay , M. Aqueous polystyrene–fluor nanosuspensions for quantifying α and β− radiation . Nanotechnology 18 ( 22 ), 22502 ( 2007 ). OpenURL Placeholder Text WorldCat 2 Harley , J. H. , Hallden , N. A. and Fisenne , I. M. Beta scintillation counting with thin plastic phosphors . Nucleonics 20 , 59 – 61 ( 1962 ). OpenURL Placeholder Text WorldCat 3 Bertrand , G. H. V. , Hamel , M. and Sguerra , F. Current status on plastic scintillators modifications . Chem. Eur. J. 20 , 15660 – 15685 ( 2014 ). Google Scholar Crossref Search ADS WorldCat 4 Miramonti , L. A plastic scintillator detector for beta particles . Radiat. Meas. 35 , 347 – 354 ( 2002 ). Google Scholar Crossref Search ADS WorldCat 5 Furuta , E. , Ohyama , R. , Yokota , S. , Nakajo , T. , Yamada , Y. , Kawano , T. , Uda , T. and Watanabe , Y. Measurement of tritium with high efficiency by using liquid scintillation counter with plastic scintillator . Appl. Radiat. Isot. 93 , 13 – 17 ( 2014 ). Google Scholar Crossref Search ADS PubMed WorldCat 6 Furuta , E. and Kawano , T. A plastic scintillation counter prototype . Appl. Radiat. Isot. 104 , 175 – 180 ( 2015 ). Google Scholar Crossref Search ADS PubMed WorldCat 7 Miyoshi , H. and Ikeda , T. Preparation of paper scintillator for detecting 3H contaminant . Radiat. Prot. Dosim. 156 ( 3 ), 277 – 282 ( 2013 ). Google Scholar Crossref Search ADS WorldCat 8 Stober , W. and Fink , A. Controlled growth of monodisperse silica spheres in the micron size range . J. Colloid Interface Sci. 26 ( 1 ), 62 – 69 ( 1968 ). Google Scholar Crossref Search ADS WorldCat 9 Browne , E. and Firetone , R. B. Table of Radioactive Isotopes ( New York : Wiley-Interscience Inc ) ( 1986 . Lawrence Berkeley Laboratory University of Calfornia. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 10 Gledhill , J. The range-energy for 0.1–600 keV electrons . J. Phys. A 6 , 1420 – 1428 ( 1973 ). Google Scholar Crossref Search ADS WorldCat 11 The costs of all the original chemicals used in the preparation are as follows: silica FP, $0.0019; sodium silicate solution, $1.15; POPOP, $0.41; PPO, $0.96; benzoic acid, $0.036; DMSO, $0.84; ethyl alcohol, $3.52; TEOS, $0.63; conc. NH4OH, $0.034; the sum is $7.58. This cost is for 3.3 g of scintillator–silica FPs; the final cost of 50 mg of scintillator–silica FPs is about $0.11. 12 Buck , C. , Gramlich , B. and Wagner , S. Light propagation and fluorescence quantum yields in liquid scintillators . J. Lumin. 10 , P09007 ( 2015 ). OpenURL Placeholder Text WorldCat © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com
TI - Preparation of New Scintillation Imaging Material Composed of Scintillator–Silica Fine Powders and its Imaging of Tritium
JF - Radiation Protection Dosimetry
DO - 10.1093/rpd/ncw251
DA - 2017-05-01
UR - https://www.deepdyve.com/lp/oxford-university-press/preparation-of-new-scintillation-imaging-material-composed-of-IULIYiWgM3
SP - 478
VL - 174
IS - 4
DP - DeepDyve
ER -