bluuebunny/crossref_metadata_2025_split huggingface dataset:
UV-Blue Emitting SiO2 Sintered Glass for Radiation Dosimetry
Authors: Okada Go , Kawaguchi Noriaki , Yanagida Takayuki 
Published: February 2020

Phosphor materials are often used in radiation measurement as a converter, from ionizing radiation to light. In dosimetry, a phosphor material absorbs and accumulates the incident radiation energy over a certain period of time as electronic charges trapped at localized centres. A recombination of these charges can be stimulated externally by light exposure or heat, followed by light emission. The latter emission intensity is proportional to the incident radiation dose accumulated, hence the radiation dose can be indirectly measured. Today, such phosphor materials are used in a variety of scenes, for example, personnel dose monitoring, radiation therapy, and medical imaging.
In this study, we have synthesized bulk SiO2 glasses and characterized for dosimetry applications. The samples were prepared by spark plasma sintering (SPS), which is a unique way to obtain a bulk SiO2 glass. First, radioluminescence (RL) spectrum was measured for both the prepared sample and SiO2 single crystal. The glass sample showed a broad emission feature from 300 to 500 nm while the crystal sample showed a narrower emission around 450 nm. The RL measurement at low temperatures revealed that the broad emission by glass consists of two components with the peaks at 385 nm and 511 nm. The origin of the former emission seems to be a pair of silylene centres generated by sintering process while the latter is due to a presence of dioxasilirane and sililene. Moreover, it was found that the sample shows a strong thermally-stimulated luminescence (TSL) after X-ray irradiation. The glow curve indicates strong emissions at the temperatures of approximately 140 °C and higher than 300 °C. In contrast, SiO2 single crystal shows much weaker signal at lower temperature (~90 °C). The luminescent centres responsible for TSL are the silylene-silylene pair emitting at 385 nm. With a use of TSL in our SiO2 glass sample, a detectable X-ray dose range is at least 1 - 10000 mGy, which is a comparable sensitivity to commercial dosimeter.
Scintillation and Dosimeter Properties of MgO Transparent Ceramic Doped with C
Authors: Kato Takumi , Okada Go , Yanagida Takayuki 
Published: February 2020

From the view point of MgO for radiation detector uses, in the 1970s, undoped MgO powder was found to show dosimeter properties. When it was irradiated by X-ray, γ-ray and UV, two TSL glow peaks were found around 90-100 and 140 °C [1]. Furthermore, in the later decades, MgO have been intensively studied for dosimeter applications due to the bioequivalency [2].
In this study, we synthesized a series of transparent ceramic MgO doped with 0.001, 0.01 and 0.1% of C by a Spark Plasma Sintering (SPS) method and studied scintillation and dosimeter properties against X-rays. The C-doping is inspired by C-doped Al2O3crystalline powder used for a personal dosimeter [3]. Recently, it was pointed out that scintillation and dosimeter are complementarily related in some material systems [4] so investigations of both the dosimeter and scintillation properties are important to understand the luminescence phenomena induced by ionizing radiations.
In the scintillation spectra, the emission bands were detected around 400 and 760 nm, and the origins of these peaks were assigned in previous reports [5]; therefore, we think that emission peaks around 400 and 760 nm may be due to F+ center and Cr3+ ion impurity, respectively. Moreover, the emission peak was also observed at 330 nm and it is said that its origin related to surface (grain boundary) defect [6]. Compared with the scintillation spectrum of the undoped MgO transparent ceramic in Ref [5], 330 and 400 nm peak intensities increased while 750 nm peak intensity decreased with C-doping. This result suggests two possibilities; a first one is that electrons are hard to transport to Cr3+ ion because C-doping generated F+ center and surface defect acting as emission center newly. The number of generated careers are finite, and if most careers recombine at these defect emission centers, Cr3+emission should be reduced. A second one is that defects generated by C-doping simply act as trapping centers, and in this case, careers would be stored.

H. Nanto, K. Inabe, H. Yamazaki and N. Takeuchi, J. Phys. Chem. Solid.,
36 477 (1975).

C. Soliman, Radiat. Eff. Defect. S., 164 257 (2009).

S.W.S. McKeever, Radiat. Meas., 46 1336 (2011).

T. Yanagida, J. Lumin., 169 544 (2016).

T. Kato, G. Okada, T. Yanagida, Ceram. Int., 42 5617 (2016).

F. Gu, et al., J. Alloy. Compd., 453 361 (2008)
Thermal Neutron Response of Tungsten Doped Lithium Fluoride Single Crystal
Authors: Kawaguchi Noriaki , Okada Go , Yanagida Takayuki 
Published: February 2020

The He-3 supply crisis have currently caused demand of alternative neutron detectors of He-3 gas filled proportional counters. One of the alternative detectors is a scintillation counter which consists of a solid neutron scintillator and a photodetector such as a photomultiplier tube (PMT). The LiF:W single crystal is known as a scintillation material and contains Li-6 which convert thermal neutrons into high energy charged particles. However, neutron scintillation properties of LiF:W were not clear because there were no comparative studies with other traditional neutron scintillators.
In this study, photo-luminescence (PL) properties, X-ray excited radio-luminescence (XRL) properties and pulse height spectra under thermal neutron irradiation of LiF:W single crystal (diameter, 25.4 mm; thickness, 25.4 mm) were evaluated. At the same time, ones of Li-glass scintillator were also measured as a reference. From PL spectra under 250 nm UV light excitation and XRL spectra, emission peaks of LiF:W and Li-glass were observed at around 440 nm and 400 nm, respectively. Bialkali PMTs are sensitive to these wavelengths. PL quantum yields of LiF:W and Li-glass were 25.8% (under 250 nm UV light excitation) and 80.1% (under 340 nm UV light excitation), respectively. PL and XRL decay curves of LiF:W were also measured and both decay times were several tens of micro second. On the other hand, decay time of Li-glass is reported less than 100 ns. As a result of evaluation of pulse height spectra of LiF:W and Li-glass under thermal neutron irradiation, thermal neutron events were successfully observed by using both materials. In case of using LiF:W, we obtained a broad detection peak around the thermal noise level of PMT. This result will be explained with low PL quantum yields and slow decay time of LiF:W.
A Study on Synthesis of SrLu2O4:Eu2+ Red Phosphor and Its Photoluminescence Properties
Authors: Kim Kyeong-Ho , Kang Eun-Hee , Hong Seong-Hyeon 
Published: February 2020

During the last decades, rare-earth (RE) ion-doped phosphors have received much attention due to their high luminescent properties. For this reason, many studies have been focused on new composition of phosphor with high luminescent properties. Eu3+ doped SrLu2O4, which is a new composition phosphor, has been reported to describe the luminescent properties. Upon excitation with ultraviolet (UV) regions, Eu3+ doped SrLu2O4 phosphor exhibited narrow red emissions due to the 4f-4f transition of Eu3+ ions. Eu3+ ions only can be excited with UV regions and the property of narrow red emission has a limitation to apply for lighting devices such as white light-emitting diodes (WLEDs) due to a low color rendering index (CRI).
In this study, we synthesize the Eu2+ doped SrLu2O4
red phosphors with solid-state reaction and characterize the luminescent properties for the first time. For the synthesis of SrLu2O4 at stoichiometric condition, it is hard to synthesize the pure SrLu2O4 phase, because formation of a second phase Lu2O3 were consistently unable to avoid. The pure phase of SrLu2O4 was formed at certain ratio of starting materials and annealing temperature conditions. The mixtures were annealed at various temperatures (1400–1600 °C) for 3 hours under 5% H2/N2 atmosphere in order to reduce Eu3+ to Eu2+.
Upon excitation with 450 nm, the synthesized SrLu2O4:Eu2+ phosphors exhibited a strong red emission centered at 610 nm due to the 4f-5d transition of Eu2+ ions (Figure 1). SrLu2O4:Eu2+ phosphors showed highest PL intensity at very low europium doping level, which intensity value was 85% of commercial (Sr,Ca)AlSiN3:Eu2+ (SCASN). In addition, SrLu2O4:Eu2+ phosphors also showed a strong thermal quenching property, which indicated that PL intensity measured at 200 oC was reduced to almost zero per cent of the initial value (25 oC). These high value of PL intensity and strong thermal quenching property can be used as a high potential optical temperature sensor application.

Figure 1
Relationship Between, the Centroid Shift of Eu2+ and Ce3+ with the Band Gap of the Host Lattice
Authors: Camardello Sam Jospeh , Srivastava Alok M , Toscano Paul J , Setlur Anant A 
Published: February 2020

In this the talk the relationship between the centroid shift of Ce3+ and Eu2+ and the host lattice exciton energy is discussed. Combining this relationship with the dependence of the crystal field splitting on the coordination polyhedral [1] can define the excitation spectra of Ce3+ and Eu2+ in a given host lattice.
Figure 1: The Centroid shift vs. the host lattice exciton energy for Ce3+ and Eu2+

[1] P. Dorenbos, J. Phys.: Condens. Matter, 15, 4797 (2003).

Figure 1
Photoluminescence Properties and Energy Transfer in Color-Tunable Garnet Phosphor for High Quality LED Lighting
Authors: Won Seob , Arunkumar Paulraj , Im Won Bin 
Published: February 2020

Recently, the performance of phosphor-converted white light-emitting diodes (WLED) has been improved mainly by diversifying the components, encapsulation of the device, phosphor synthesis, as well as designing new strategies for the development of phosphors. Nowadays, single-composition white-emitting phosphors which are excited by near UV or blue LED have been developed to prevent the reabsorption, instability of color temperature, and cost issues.
We report a garnet phosphor with partially displaced Tb3+ and Pr3+ as green and red components respectively. A green-emitting and white-emitting phosphor was synthesized by a solid-state reaction, exhibiting an efficient green emission and red emission at 543 nm and 609 nm under blue excitation. The structural and optical properties of the phosphor were studied using powder X-ray diffraction and photoluminescence analysis. The compound crystalizes in cubic phase with space group Ia
d. The partial substitution of Tb3+ and Pr3+ in garnet phosphor led to a considerably broad emission spectrum. The WLED was fabricated by using phosphor-in-glass with a blue LED chip and exhibited a warm white light with an excellent color rendering index of 92. The garnet phosphor with Ce3+, Tb3+, and Pr3+ is thus a potential green and white-emitting phosphor for LED lighting.
Figure 1. PL excitation and emission spectrum of garnet phosphor with (a) Ce3+, (b) Ce3+, Tb3+, and (c) Ce3+, Pr3+.

Figure 1
Synthesis of New Melilite Structured Blue Phosphor for UV LED
Authors: Kim Ha Jun , Im Won Bin 
Published: February 2020

Solid-state LED lighting has been in the spotlight due to its high efficient, energy savings, and eco-friendly nature. Conventional blue LED based white lighting in combination with yellow phosphors showed high luminous efficiency (>30 lm/W) but have serious issue of poor color rendering index (65) due to weak red emission. As an alternative, UV based white LEDs has been under intensive research due to its high color rendering index (99), excellent conversion efficiency and a wide emission band ranging 350 to 700 nm.
In this study, a blue-emitting melilite phosphor was developed with wide absorption in the near-UV by solid-solution. The synthesized blue phosphor has wide absorption band with a maxima at 420 nm. The emission wavelength was tunable in the window of 470 to 505 nm. The structural and optical characteristics were investigated using X-ray diffraction, Rietveld refinement, photoluminescence, thermal quenching and decay time. Finally white LED was fabricated using the optimized melilite blue phosphor in combination with commercial green and red phosphor under 420 nm LED chip. The results indicate melilite blue phosphor could be promising blue component for UV based white LEDs.
Fig1. Normalized excitation and emission spectra of the Sr4-x-y
Ca
­x
Ba
y
MgAl2Si3O14:Eu2+

Figure 1
(Invited) Discovery and Structural Design of New LEDs Phosphors
Authors: Xia Zhiguo 
Published: February 2020

Phosphor materials enable the wavelength conversion to realize the full-color white emission light-emitting diodes (LEDs). So far much effort has been devoted to the design and discovery of novel LED phosphors for solid state lighting. Understanding and exploring the structural design principles of the inorganic hosts are necessary for the discovery of novel LED phosphors. Our recent work focuses on the discovery of new phosphor materials based on the structural evolution and the crystallographci sites engineering. Firstly, photoluminescence tuning can be realized via the cation substitution on one site, and hereby we have discovered several types of M2SiO4-based and M3(PO4)2-based phosphors with tunable emission for white LEDs.1-2 Secondly, we have recently proposed the concept of “chemical unit cosubstitution” as one potential design scheme, and the chemical unit cosubstitution strategy is applied to the melilite structure class designing the Ca2(Al1−x
Mg
x
)(Al1−x
Si1+x
)O7:Eu2+ solid solution phosphor via the [Mg2+−Si4+] for [Al3+−Al3+] cosubstitution.3 We also design the La5Si3O12N phase from La5Si2BO13 via the [B3+−O2−] by the [Si4+−N3−] cosubstitution.4 Thirdly, we have proposed a new insight into the design of the isostructural phases via the filling of M+ in the void channels of the Mg2Al4Si5O18 phase, so that the charge balance can be kept while the chemical composition varied, and this strategy will be also efficient in other porous inorganic hosts.5 Finally, we have recently studied the NaScSi2O6-based phosphor from CaMgSi2O6-based phosphor via the chemical unit cosubstitution of [Na+–Sc3+] for [Ca2+-Mg2+] unit.6 Further studies show that the isostructural solid-solution of (CaMg)
x
(NaSc)1-x
Si2O6 (0 < x < 1) can be formed, in which cation nanosegregation enables the presence of dilute Eu2+ at two centers and their intensities are linearly proportional to x, so that it represents a new cation nanosegregation tuning of photoluminescence for the exploration of color-tunable phosphor for white LEDs.7-8

References

[1] Z. G. Xia*, et. al., Inorganic Chemistry, 2015, 54, 7684-7691. (Cover paper)
[2] Z. G. Xia*, et. al., Journal of Physical Chemistry C, 2015, 119, 2038–2045.
[3] Z. G. Xia*, et. al., Journal of the American Chemical Society, 2015, 137, 12494-12497.
[4] Z. G. Xia*, et. al., Journal of Physical Chemistry C, 2015, 119, 9488–9495.
[5] Z. G. Xia*, et. al., Scientific Reports, 2015, 5, 12149.
[6] Z. G. Xia*, et. al., Journal of Physical Chemistry C, 2013, 117, 20847−20854. (Cover Paper)
[7] Z. G. Xia*, et. al., Scientific Reports, 2013, 3, 3310-3310-7.
[8] Z. G. Xia*, et. al. Journal of the American Chemical Society, 2016, 138, 1158-1161.
(Invited) Investigation of Blue Excitation Flux Dependent Conversion Efficiency in Phosphors for High Luminance Applications
Authors: Raukas Madis , Avallon James , Kelso John , Lenef Alan , Wang Jingzhou 
Published: February 2020

Solid State Lighting (SSL) devices based on phosphor conversion have significantly evolved on a scale of output flux and white light luminance and extend now to the range where competition with the brightest arc discharge-based sources is ongoing. Such sources are unique in the SSL world in that they provide both an expanded emission spectrum and high luminance. The efficiency of high luminance semiconductor pumped phosphor sources depends not only on efficient generation of primary radiation from the semiconductor (LEDs or laser diode), but also strongly on the conversion material which is being pushed to optical and thermal limits. Such conversion materials are typically operating under heavy irradiance and thermal load and nearly always exhibit sublinear behavior in output at high input fluxes, due to a multitude of reasons. In the present study, we have separated contributions from thermal and non-thermal quenching mechanisms, in particular investigated phosphor saturation, or excitation quenching, in the converter light output as a function of blue pump intensity. It is important here to distinguish between the true loss mechanisms (for example via Auger-like or excited state absorption processes [1-6]) and the reduction in converted output due to increased transparency for the pump light (e.g. activator ground state depletion). We discuss the behavior of measured conversion efficiency as a function of excitation intensity (and parameters like temperature, activator type and concentration or host material). A model is proposed to explain the observed dependencies in different host-activator systems.
[1] W.J. Miniscalco et al, J.Appl.Phys., 49, 6109 (1978)
[2] D.S. Hamilton et al, Phys.Rev.B 39(13), 8807 (1989)
[3] K. Wisniewski et al, Acta Phys. Polonica A, 95(3), 403 (1999)
[4] K.C. Mishra et al, J.Electrochem.Soc. 151(5), H105 (2004)
[5] A. Lenef et al, SPIE 884107 (2013)
[6] O.B. Shchekin et al, Phys.Status Solidi RPL 1-5 (2016)
(Invited) Phosphor-in-Glass Luminescent Materials for Solid State Laser Lighting
Authors: Xie Rong-Jun , Zhu Qiang-Qiang , Takeda Takashi , Hirosaki Naoto 
Published: February 2020

Laser-based solid state lighting is superior to the LED-based counterpart in terms of much high input power and lumens, which requires phosphors to be more thermally stable and less luminescence saturation under high-density laser irradiations. To minimize thermal quenching and luminescence saturation of phosphors, a revolutionary method is to apply phosphor-in-glass or ceramic phosphors rather than phosphor-in-silicone (polymer binder) in remote-phosphor technologies because bulk luminescent materials have higher thermal conductivity and less degradation than phosphor/silicone mixtures.
In this work, we will report the preparation and optical properties of nitride phosphor-in-glass luminescent materials. The nitride phosphor (β-sialon:Eu2+) was co-fired with the glass frit in the system of ZnO-B2O3-Ba2O3-Al2O3 at 630-650oC. No interfacial reaction occurred during the co-firing. The quantum efficiency and transmittance of the phosphor-in-glass luminescent materials were greatly affected by the phosphor concentration, firing temperature and holding time. Upon the blue laser irradiation, a linear relationship between the luminous flux and the incident laser power was observed when the flux density was below 0.7 W/mm2. A serious luminescence saturation was seen when a high flux density was applied. The saturation was perhaps due to the extremely low concentration and relatively longer decay time of Eu2+. This phosphor-in-glass luminescent materials could be used for low-power solid state laser lighting.
(Keynote) Advanced Platform Technologies for the Near Future Electrochemical Biosensing
Authors: Sode Koji 
Published: February 2020

Glucose sensing is the most popular analytical method in the use of the electrochemical biosensing technology. Simultaneously, it is one of the most popular, commercial available, and commoditized biotechnology relating products, where the most advanced but economical materials and technologies are utilized. Current market products in the glucose sensors for the self-monitoring of blood glucose (SMBG) or in the continuous glucose sensing (CGM) systems, the electrochemical principle, either the “1st generation”, which utilizes oxygen as the electron acceptor, or the “2nd generation” principles, which utilizes artificial electron acceptors, has been employed. All other sensing targets by the biochemical analyses in the metabolic disorder syndromes, such as cholesterol, neutral lipid, uric acid, glycated proteins, amino acids, lactates, etc., are also being electrochemically measurable based on these principles, and some are already commercially available.
However, recent emergent requirement in the development of accurate and precise sensing systems, which meet the strict regulation with competitiveness in the harsh market of blood glucose monitoring, accelerate the demands in the development of novel platform technologies in the electrochemical biosensing system, which are ready to use in the market grade product.
In this presentation, I introduce three indispensable platform technologies which accelerate the development of the near future electrochemical biosensing, especially in the amperometric enzyme sensors; 1) engineered flavin dependent oxidoreductases, 2) disposable interdigitated electrode, and 3) a novel artificial electron acceptor (mediator).
Molecular Dynamics Simulation of Substrate Transport on Alpha-Helix Peptide for Multistep Catalysis
Authors: Liu Yuanchao , Calabrese Barton Scott 
Published: February 2020

Multistep electrocatalysis has the potential to fully utilize the energy stored in high molecular weight fuels, enabling biofuel cells with high energy density.[1] In multistep cascades, however, the mass transport of intermediates between catalyst sites becomes a potential limitation. Substrate channeling, in which intermediate transport is achieved without diffusion into the bulk, has attracted significant attention recently and is utilized in numerous biological contexts.
Electrostatic interactions between a charged intermediate and an oppositely charged pathway represents on such channeling mechanism.[2] Molecular Dynamic (MD) simulation enables the study of electrostatic interactions that may be inaccessible to experiment, and provides a framework for molecular design of such systems. Here, we describe MD simulations of charged intermediate transport in the presence of alpha-helix peptides that act as catalyst site linkers.[3] In this project, we generated a set of polypeptides comprised of charged residues chains (e.g. Arg, Lys) and simulate the interaction between these peptides and oppositely charged intermediate molecules in explicit water. Figure 1a shows an example on how an oxalate molecule can be adsorbed on a peptide, featuring corresponding coulomb energy between the two species. Strong energy fluctuations usually indicate surface-bound transport. By tuning the side chain type and interspatial distance, as shown in Figure 1b, energy fluctuation can be controlled. Based on the results from different peptides coupled with various intermediate molecules, we are able to define the range of conditions over which electrostatic interactions are beneficial. More importantly, surface diffusion diffusion is quantified, giving detailed understanding of the range of transport rates available. Acknowledgement We gratefully acknowledge support from Army Research Office MURI (#W911NF1410263) via The University of Utah. References [1] M. J. Moehlenbrock, M. T. Meredith, and S. D. Minteer, ACS Catal., 2, 17–25 (2012) doi:10.1021/cs200482v. [2] I. Wheeldon et al., Nat. Chem., 8, 299–309 (2016) doi:10.1038/nchem.2459. [3] J.-L. L. Lin and I. Wheeldon, ACS Catal., 3, 560–564 (2013) doi:10.1021/cs300766d. Figure 1. MD simulation of oxalate molecule (-2 charged) on alpha-helix peptide with +1 charged side chains (e.g., Arg and Lys). a) Oxalate molecule (red) on peptide with Arg side chains marked in blue (Arg-6*Ala-Arg-6*Ala-Arg-3*Ala), clearly showing various adsorption configuration and corresponding calculated coulomb energy. b) Oxalate molecule on peptide with more dense Lys side chains (3*Ala-Lys-3*Ala-Lys-3*Ala-Lys-3*Ala), featuring an adsorption region with frequent coulomb energy fluctuation and showing substrate transport along the helical axis of peptide.

Figure 1