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In this study, we report the fabrication and characterization of a 3D printed polyvinyl toluene based plastic scintillator by DLP (digital layer print) 3D printer. The homemade resin has been used for 3D printing. The organic solvents such as vinyl-toluene monomer, PPO (2,5-Diphenyloxazole), POPOP [1,4-bis(5-phenyloxazol-2-yl) benzene], pentaerythritol tetrakis (3-mercaptopropionate), and DHPA (dipentaerythritol hexa-acrylate) have been used as co-polymers. Irgacure 184 (BASF Co.) is used as photo-initiator. Using DLP 3D printer (http://attosystem.co.kr) and the prepared resin, a plastic scintillator is printed. The emission spectrum of the printed plastic scintillator is located between 400 and 600 nm, peaking at 424 nm. The relative light yield of the scintillator is about 80% of EJ-200, relatively, and the decay time is about 3.9 ns.

The paper discusses the possible processes of radiation-induced changes that occur during irradiation of composite scintillators containing grains of inorganic crystals, and investigates the effect of these processes on radiation resistance of composite systems. All crystalline inorganic scintillation materials contain defects, which can play the role of quenching centres. An irradiation destroys and changes not only the main material of a scintillator but such the centres as well. As a result, the luminescence intensity can grow for a while due to weakening the effect of quenching. In this case, the luminescence spectrum of a scintillator does not change its shape under various accumulated doses D because no new luminescence centres appear. A modification of the properties of the luminescence centres arising under the action of irradiation has to lead to a change in the spectral characteristics of the luminescence. Therefore, the appearance or absence of such the changes is evidence of which centres are predominantly damaged because of irradiation with given dose D. The paper as well discusses the possibilities of obtaining radiation-resistant materials for the development of wavelength shifting light guides for composite scintillators. We investigated samples based on non-luminescent transparent silicone elastomer containing p-terphenyl or 1,4-di[2-(5-phenyloxazolyl)]benzene (POPOP) molecules.

We report herein the synthesis of a new series of plastic scintillators (PSs) loaded with 6Li210B4O7 nanoparticles (NPs), as new radioluminescent sensors for fast/thermal neutron and gamma ray detection in the critical context of homeland security. This study aims to evaluate the benefit of such nanoparticles towards thermal neutron detection in a fast neutrons/gamma discriminating PS composition. First, a size-controlled synthesis of Li2B4O7 NPs assited with poly(N-vinylpyrrolidone) (PVP) is performed. Then enriched 6Li210B4O7 NPs (65 ± 22 nm) are dispersed in clear PSs mainly composed of polystyrene and standard fluorophores (20 wt% PPO, 0.03 wt% POPOP). For the first time, a triple nthermal/nfast/gamma discrimination is presented with a NP-loaded plastic scintillator, where both 6Li(n,α) and 10B(n,α) are observed.

A series of nanostructured organosilicon luminophores (NOLs) composed of a central 1,4-bis(5-phenyl-1,3-oxazol-2-yl)benzene (POPOP) acceptor chromophore and various peripheral p-terphenyl and 2,5-diphenyl-1,3-oxazole donor fragments have been synthesized for the first time using van Leusen reaction and direct palladium-catalyzed C-arylation of oxazole ring. Due to different functionalities of the silicon branching centers, NOLs with different donor-acceptor ratios have been obtained. The synthesized structures are expected to possess good optical characteristics for use in photonics and optoelectronics.

6Li-Doped plastic scintillators (PSs) have been optimized as radioluminescent sensors for detection of fast/thermal neutrons and gamma rays for several purposes such as homeland security. Among 16 low molecular weight (C < 8) lithium carboxylates, Liα-valerate (LiαVal) exhibits high potential for loading (up to 50 wt%) in clear PSs composed of polystyrene and standard fluors (20 wt% PPO, 0.03 wt% POPOP). A methodical study of PS composition illustrates that the Li carboxylates and methacrylic acid comonomers impact the scintillation yields (from 4410 to 7790 ph per MeV) and nthermal/nfast/gamma discrimination performances with significant figures of merit (from 0.23 to 1.45 above 180 keVee).

The highly reliable and direct detection of radioactive cesium has gained potential interest due to in-situ detection and monitoring in environments. In this study, we elucidated an integrated and portable probe based on functional plastic scintillator for detection of radioactive cesium. A functional plastic scintillator with improved detection efficiency was fabricated including CdTe (cadmium telluride) material. Monolith-typed functional plastic scintillator having a diameter of 50 mm and a thickness of 30 mm was manufactured by adding 2,5-diphenyloxazole (PPO, 0.4 wt%), 1,4 di[2-(5phenyloxazolyl)]benzene (POPOP, 0.01 wt%), and CdTe (0.2 wt%) materials in a styrene-based matrix. To evaluate the applicability of the plastic scintillator manufactured to in-situ radiological measurement, an integrated plastic detection system was created, and the measurement experiment was performed using the Cs-137 radiation source. Additionally, detection efficiency was compared with a commercial plastic scintillator. As results, the efficiency and light yield of a functional plastic scintillator including CdTe were higher than a commercial plastic scintillator. Furthermore, the remarkable performance of the functional plastic scintillator was confirmed through comparative analysis with Monte Carlo simulation.

Luminescence and kinetic characteristics of polystyrene nanocomposites with luminescence impurities of p-Terphenyl, POPOP and CeF 3 nanoparticles were studied. Intensity of X-ray excited luminescence of the polystyrene scintillation composites containing CeF 3 nanoparticles (40 wt%) has been established to substantially increase (up to 16 times), mainly due to excitation energy transfer from the CeF3 nanoparticles to the polystyrene matrix by means of the electron escape mechanism.

In this article the properties of four new luminophores, from the group of bifluorenes and other substances with multiple aromatic rings, were measured and studied for possible use in liquid scintillation, namely 1-phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline, 2,2′,7,7′-tetrakis(N,N-diphenyl-amino)-9,9′-spirobifluorene, 2-(4-biphenylyl)-6-phenylbenzoxazole and 9,9′-bifluorenyl. The measurement was also done for the most commonly used luminophore (2,5-diphenyloxazole (PPO)). To improve counting efficiency the wavelength shifters were added to scintillation cocktail in particular POPOP and bis-MSB. The main effort was focused on the determination of sample counting efficiency of experimental cocktails using radionuclides Am-241, Sr-90 and H-3, especially for acidic, alkaline and neutral water solutions. The results were compared with the commercially used Aqualight scintillation cocktail.

This paper deals with the study of 1-phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline, 2,2´,7,7´-tetrakis(N,N-diphenyl-amino)-9,9´-spirobifluorene, 2-(4-biphenylyl)−6-phenylbenzoxazole and 9,9´-bifluorenyl as possible replacements of the existing and most widely used luminophore (2.5-diphenyloxazole (PPO)) in contemporary scintillators. The study is focused on the determination of emission wavelength, concentration optimization, the influence of the wavelength shifters POPOP and bis-MSB. In addition, the response to alpha and beta radiation were measured, in particular, the pulse length index (PLI) was determined. Finally, yet importantly, the effect of emulsifiers on the shape of the spectrum and the solubility of the aqueous phase was tested. The results obtained were compared with the commercially available Aqualight scintillation cocktail.

Composite films of CdWO4 embedded in polystyrene have been prepared and characterized through microtomography, photoluminescence and X-ray excited optical luminescence. CdWO4 scintillator powder was successfully produced via microwave-assisted hydrothermal method using oxide precursors. With the control of synthesis pH, CdWO4 wolframite structure was obtained at temperatures as low as 100 °C for reaction time of 1 h. Surface modification of CdWO4 particles by stearic acid promoted good dispersion of scintillator nanoparticles within the polymeric matrix. The composites have been prepared with 220 µm or 440 µm thickness and CdWO4/PS mass ratios of 10% and 20%. Optical measurements show the characteristic CdWO4 emission in the blue region as well as PS luminescence due to PPO, POPOP and PTO organic impurities. Under X-ray excitation, the light output was proportional to the increase of scintillator content and sample thickness. The emission intensity varied for each film face irradiated, being the most homogeneous condition achieved for the composite of 440 µm and CdWO4/PS = 10%.

Phosphorus (P) is an essential element for all organisms and thus the P cycle plays a key role in determining the dynamics of lower trophic levels in marine ecosystems. P in seawater occurs conceptually in particulate and dissolved organic and inorganic (POP, PIP, DOP, and DIP, respectively) pools and clarification of the dynamics in these P pools is the basis to assess the biogeochemical cycle of P. Despite its importance, behaviors of each P pool with phytoplankton dynamics have not been fully examined. We measured the four operationally defined P pools (POPop, PIPop, DOPop, and SRP) during an iron-induced phytoplankton bloom (as part of the subarctic ecosystem response to iron enrichment study (SERIES)) in the eastern subarctic Pacific in summer 2002. During our observations of the iron-enriched patch from day 15 to day 26 after the iron infusion, chlorophyll-a concentration in the surface layer decreased from 6.3 to 1.2 μg L− 1, indicating the peak through decline phase of the phytoplankton bloom. At the bloom peak, P was partitioned into POPop, PIPop, and DOPop in proportions of 60, 27, and 13%, respectively. While chlorophyll-a and POPop showed similar temporal variations during the declining phase, PIPop showed a different peak timing with a 2 day delay compared to POPop, resulting in a rapid change in the relative proportion of PIPop to total particulate P (TPP = POPop + PIPop) at the peak (25%) and during the declining phase of the bloom (50%). A part of POPop was replaced by PIPop just after slowing down of phytoplankton growth. This process may have a significant role in the subsequent regeneration of P. We conclude that measurement of TPP alone is insufficient to show the interaction between P and phytoplankton dynamics and fractionation of TPP into POPop and PIPop provides useful insights to clarify the biogeochemical cycle of P.

In this work, a versatile synthetic method for preparation of linear phenyloxazoles and their organosilicon derivatives under mild conditions via a combination of van Leusen and direct C H arylation reactions is reported. It was used for the synthesis of a novel trimethylsilyl (TMS) derivative of blue laser dye 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP) and its structural isomer 1,4-bis(2-phenyloxazol-5-yl)benzene (isoPOPOP) with and without TMS substituents. All of the compounds demonstrated high photoluminescence quantum yields and large molar extinction coefficients, which further increased for their TMS derivatives. Measurements of accelerated photodegradation of the dyes in diluted THF solutions revealed that POPOP-type compounds are twice more stable than their isoPOPOP-type isomers, independent of the presence or absence of TMS substituents. Cyclic voltammetry (CV) investigations revealed that POPOP-type dyes are more electrochemically stable as compared to their isoPOPOP-type isomers. Quantum chemical TD DFT calculations of the frontier energy levels of the dyes were in a good agreement with the experimental data obtained by CV. Single-crystal X-ray diffraction experiments revealed significant structural differences between crystal lattices of the dyes. Due to facile synthesis and excellent optical properties as well as high photo- and thermo- stability the novel luminescent dyes may find wide application in organic photonics.

A series of polystyrene-based scintillators have been prepared by thermal polymerization without any initiators. To investigate the influence of the primary additive and wavelength shifter on the performance of plastic scintillator, two primary additives and four wavelength shifters were added to the scintillators, respectively. The results showed that 2,5-diphenyloxazole (PPO) and 5-phenyl-2-[4-(5-phenyl-1,3-oxazol-2-yl)phenyl]-1,3-oxazole (POPOP) were the most adequate fluorescent dyes for initiator-free preparation of the polystyrene-based scintillators. The plastic scintillator containing 1% PPO and 0.02% POPOP possessed the highest fluorescence intensity. Initiator-containing polystyrene-based scintillator with the same concentration of PPO and POPOP (1% PPO, 0.02% POPOP and 0.01% AIBN) was also prepared. The light yield of the plastic scintillator without any initiators is 83.49% relative to the value of the standard sample EJ-200, which is higher 8% than that of initiator-containing plastic scintillator. Moreover, compared with the standard sample EJ-200 with a decay time of 2.09 s, the decay time of the initiator-free and initiator-containing plastic scintillator was 1.80s and 1.86 s, respectively.

To investigate the influence of both the first luminescent additive and the wavelength-shifter on the performance of plastic scintillator, a series of polystyrene-based scintillator had been prepared by thermal polymerization. Three first luminescent additives (PPO, p-TP and b-PBD) and four wavelength-shifters (POPOP, Bis-MSB, Me-MSB and DPA) were added to the scintillators respectively. The comparison results showed that PPO and POPOP were the most adequate fluorescent dyes for the polystyrene-based plastic scintillator. Moreover, with the increase of the concentration of PPO and POPOP, the fluorescence intensity and light yield were increased firstly and then decreased. The plastic scintillator containing 2% PPO and 0.02% POPOP had the highest fluorescence intensity and light yield.

New composite scintillation detectors were obtained by incorporation of PPO and o-POPOP organic scintillators into porous sol–gel silica matrices. Composites possess high photoluminescence intensity and decay time in nanosecond range. The absolute light yield of composite scintillators at excitation by alpha-radiation is about 4000–5000 photons/MeV and the pulse–height resolution is about 30%. The investigations of time-resolved luminescence of composites performed under excitation by synchrotron radiation in the 3.7–25 eV range have shown that the non-radiative energy transfer between host matrix and dopant molecules occurs via singlet states of SiO2 oxygen-deficient centers.

A novel UV-curable plastic scintillator was first prepared by using the technology of photosensitivity rapid prototyping. It used the copolymer of 621A-80, TPGDA and styrene as the matrix doped with PPO and POPOP. Its fluorescence spectra displayed a maximum emission wavelength at 428 nm. The light yield of the plastic scintillator was approximately 7.1% of anthracene on the basis of a comparison with the commercially available scintillator (ST-401). The as-prepared plastic scintillator also displayed a fast scintillation decay. Its decay time is 2.6 ns approximately. Importantly, through the technology of photosensitivity rapid prototyping, the plastic scintillator could be prepared in a short period of time at low temperature. What׳s more, this preparation method provides the possibility of combining the plastic scintillator with 3D printing technology, and then the applications of the plastic scintillator may be expanded greatly.

A readily available and inexpensive boron compound was tested as an additive for the detection of thermal neutrons in plastic scintillators. Bis(pinacolato)diboron (B 2 Pin 2 ) was determined to be a compatible boron source (8.51 wt% boron, 1.70 wt% 10 B) in poly(vinyltoluene) based matrices. Plastic scintillator blends of 1–20 wt% 2,5-diphenyloxazole (PPO), 0.1 wt% 1,4-bis(5-phenyloxazol-2-yl) benzene (POPOP) and 1–15 wt% B 2 Pin 2 were prepared that provided optical clarity, good mechanical properties, and the capability of thermal neutron detection. Independent of B 2 Pin 2 concentration, strong 10 B neutron capture signals around 90 keV ee were observed at essentially constant light output. Increasing PPO concentration allowed for the use of pulse shape discrimination (PSD) in both fast and thermal neutron detection. High PPO concentrations appear to cause additional alpha quenching that affected the 10 B neutron capture signal. Aging effects after storage in air for several months were observed, which led to degradation of performance and in some samples of mechanical stability.

Plastic scintillators are the solid solutions of active additives to polymer matrices and widely used in various fields of science and technology such as high-energy physics, radiation chemistry, nuclear-power engineering, dosimetry and medical imaging. 2,5-diphenyloxazole (PPO) and 1,4-bis(5-phenyl-2- oxazolyl)benzen (POPOP) are the most widely used fluorescent additives (fluors) which lead to scintillation. Since the composition of the fluors determines the photon yield and optical properties of the scintillators, it is important to determine their concentration in the fabricated material. This paper describes a method, for the first time, for accurate determination of PPO and POPOP in plastic scintillators. A complete validation of the analytical procedure (sample preparation + HPLC method) has been performed using three spiking levels at 0.1, 10 and 100 mg L−1 and real plastic scintillator samples. Based on the results, calibration plots of PPO and POPOP were linear over the 0.01 to 150 mg L−1 concentration ranges. The limit of detection and limit of quantification were 0.92 and 2.80 μg L−1 for PPO and 2.11 and 6.39 μg L−1 for POPOP, respectively. The performance of the analytical procedure was also verified through the determination of fluors in a plastic scintillator fabricated via bulk thermal polymerization. As a consequence, the data indicate that the proposed analytical procedure for PPO and POPOP determination in plastic scintillators provides good linearity, sensitivity, accuracy, precision and robustness, which allows a novel, simple, fast, economical, and reliable qualitative and quantitative analysis.

Neutron detectors have diverse applications in exploring natural resources and in security systems. Because there is an increased demand for neutron detectors based on 3 He proportional counters , and 3He shortage is a concern. Hence, an alternative approach for large-scale detectors is necessary In this work, as an alternative to the 3 He proportional counters, we propose a simple method of fabricating liquid scintillators for neutron detection with mixed-organic solvents containing 6Li as liquid scintillators. 6 LiCl and the phosphors , DPO and POPOP, were added to a mixed organic solvent consisting of toluene and ethanol along with a given amount of 6Li. We succeeded to fabricate the liquid scintillators containing 6 Li with simple preparation and low cost compared to previous approaches. Further, in the measurement of the pulse height spectra, the thermal neutron peaks could be observed for the developing liquid scintillators. The light yields of the liquid scintillators were approximately 1200 photons/neutron.

In this paper, the features of the Raman spectra in diamond microcrystals were investigated. The Raman spectra in microdiamonds were characterized by high intensity due to the effects of trapped radiation and total internal reflection. A characteristic line with a frequency of 1332 cm–1 and additional bands located in the overtone region of fundamental modes was registered in the observed spectra. Raman spectra in diamond-substances composites (diamond: K2Cr2O7, NaBrO3, NaNO2, HgI2, K2CrO4, PbO, KIO3, sulfur, iodine, stilbene, triglyceride sulfate, and POPOP) were detected.

In this work, main results of spectral and energy dependences of two-photon luminescence in polycrystalline organic compounds are reported. The two-photon luminescence was excited by a repetitively pulsed laser on a yttrium aluminum garnet (YAG). This laser generated radiation at wavelengths of 266 and 532 nm. Two-photon luminescence and Raman scattering have been registered in a single measurement. We compared efficiency of two-photon luminescence and Raman scattering efficiency.

Spectral and luminescent properties of efficient and stable commercial organic dyes in solutions and polymethylmetacrilate (PMMA), absorbing and emitting in wavelength ranges 300–680 nm and 390–750 nm, respectively, are investigated. Using different excitation and registration schemes, it is demonstrated that spectral shifts of initial radiation caused by reabsorption are observed at wavelengths around 1.5 cm. The process of excitation energy transfer from the UV range to the red range of the spectrum is investigated in mixtures of 4–6 dyes of different compositions. The maximum efficiency of radiation transfer from 300 nm to 560–580 nm, exceeding the efficiency of individual fluorophores by a factor of >1.6 is obtained for mixtures of four dyes POPOP(bis-MSB)–Coumarin 30–DCM–Pyrromethene 580 (Rhodamine 11B) in PMMA.

The use of plastic scintillation microspheres (PSm) appear to be an alternative to liquid scintillation for the quantification of alpha and beta emitters because it does not generate mixed wastes after the measurement (organic and radioactive). In addition to routine radionuclide determinations, PSm can be used for further applications, e.g. for usage in a continuous monitoring equipment, for measurements of samples with a high salt concentration and for an extractive scintillation support which permits the separation, pre-concentration and measurement of the radionuclides without additional steps of elution and sample preparation. However, only a few manufacturers provide PSm, and the low number of regular suppliers reduces its availability and restricts the compositions and sizes available. In this article, a synthesis method based on the extraction/evaporation methodology has been developed and successfully used for the synthesis of plastic scintillation microspheres. Seven different compositions of plastic scintillation microspheres have been synthesised; PSm1 with polystyrene, PSm2 with 2,5-Diphenyloxazol(PPO), PSm3 with p-terphenyl (pT), PSm4 with PPO and 1,4-bis(5-phenyloxazol-2-yl) (POPOP), PSm5 pT and (1,4-bis [2-methylstyryl] benzene) (Bis-MSB), PSm6 with PPO, POPOP and naphthalene and PSm7 with pT, Bis-MSB and naphthalene. The synthesised plastic scintillation microspheres have been characterised in terms of their morphology, detection capabilities and alpha/beta separation capacity. The microspheres had a median diameter of approximately 130 μm. Maximum detection efficiency values were obtained for the PSm4 composition as follows 1.18% for 3 H, 51.2% for 14 C, 180.6% for 90 Sr/ 90 Y and 76.7% for 241 Am. Values of the SQP ( E ) parameter were approximately 790 for PSm4 and PSm5. These values show that the synthesised PSm exhibit good scintillation properties and that the spectra are at channel numbers higher than in commercial PSm. Finally, the addition of naphthalene modifies the shape of the pulses produced by alpha and beta particles leading to better alpha/beta separation.

Three plastic scintillators of 4.5 cm diameter and 2.5-cm length were fabricated for comparison with commercial plastic scintillators using polymerization of the styrene monomer 2.5-diphenyloxazole (PPO) and 1,4-bis benzene (POPOP). Their maximum emission wavelengths were determined at 426.06 nm, 426.06 nm, and 425.00 nm with a standard error of 0.2% using a Varian spectrophotometer (Agilent, Santa Clara, CA, USA). Compton edge spectra were measured using three gamma ray sources [i.e., cesium 137 (137Cs), sodium 22 (22Na), and cobalt 60 (60Co)]. Energy was calibrated by analyzing the Compton edge spectra. The fabricated scintillators possessed more than 99.7% energy linearity. Light output was comparable to that of the BC-408 scintillator (Saint-Gobain, Paris, France). The fabricated scintillators showed a light output of approximately 59–64% of that of the BC-408 scintillator.

Cu-deficient graded-zinc Cu-In-Zn-S (CIZS) quantum dots (QDs) were synthesized by a two-step solvothermal method. These CIZS QDs exhibited size and composition tunable photoluminescence characteristics with emission color tunable from greenish-yellow to orange to red with a relatively high quantum yield between 45 and 60%. Novel white-light-emitting (WLE) hybrid composite is fabricated by integrating the blue-emissive 1,4-bis-2-(5-phenyl oxazolyl)-benzene (POPOP) organic fluorophore and quaternary CIZS inorganic QDs. Integrating CIZS QDs with POPOP fluorophore resulted in series of tunable emission colors with CIE coordinates lying in a straight line between the coordinates of the end member. WLE was shown for hybrid mixture comprising 0.5 nM of POPOP and 3 mg/mL of CIZS QDs with color coordinates (0.3312, 0.3324). Thin films of this hybrid mixture in PMMA matrix coated on UV-LED or on glass substrates with UV backlit light also showed broadband WLE with ideal CIE color coordinates of (0.34, 0.33), high color-rendering index value of 92, and correlated color temperature value of 5143 K. The hybrid composite exhibit Forster resonance energy transfer cascading from POPOP to CIZS which results in emission covering the entire visible spectral range. POPOP and CIZS QDs hybrid composite is a versatile material for WLED applications.

A systematic study is reported on the monolayer characteristics of 2,2′-p-phenylenebis (5-phenyloxazol) (POPOP) mixed with arachidic acid (AA) at the air-water interface, using surface pressure versus area per molecule (π-A) isotherms complemented with absorption spectroscopy as well as scanning electron microscopy. The (π-A) isotherms of POPOP mixed with AA at different mole fractions show a plateau like region at very low surface pressure, which suggests a phase transition corresponding to a reorientation of the POPOP molecules at the air-water interface. The mixing behavior was obtained from surface pressure-area isotherms by using the surface phase rule and excess area criterion. Results show that POPOP is immiscible in AA, leading to the formation of aggregates. These observations are confirmed by ultraviolet-visible absorption spectroscopy and scanning electron microscopy. Absorption spectra of the mixed LB films reveal that I-type of aggregates play their prominent role in the mixed LB films.

Geometry optimizations of monomers were carried out with the use of Becke's three-parameter hybrid method with Lee, Yang, and Parr (B3LYP) gradient- corrected correlation functional and the standard 6-31G(d) basis set. UV-vis spectra of different naphthalene-POPOP complexes using ZINDO/S method were calculated. In these complexes, poly(methyl methacrylate) effect on chromophores was neglected and chromophores were staked. Analyzing available experimental data and obtained theoretical results, the most probable complex structure is determined. Molecular model of POPOP and naphthalene dimer corresponds to this structure. V C 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 2540-2544, 2011