bluuebunny/crossref_metadata_2025 huggingface dataset:
Ooptically and Thermally Stimulated Luminescence in x-Ray Irradiated Sn-Doped Sro-B2O3 and ZnO-P2O3 Glasses for Passive-Type Dosimeter
Authors: Nanto Hidehito , Nankagawa Ryota , Takei Yoshinori , Hirasawa Kazuki , Miyamoto Yuka , Masai Hirokazu , Masai Hirokazu , Okada Go , Yanagida Takayuki
Published: February 2020

Optically and thermally stimulated luminescence (OSL and TSL) phenomenon is based on the presence of electron and/or hole traps and luminescence centers in storage phosphor materials.  During exposure to ionizing radiation such as x-ray, γ-ray and β-ray, the traps are occupied with charged carriers such as electrons and holes that are created by irradiation with ionizing radiation.  De-trapping of these carriers requires energy.  The energy is provided by stimulating of the phosphor materials with visible or infrared light (OSL) or by heating of the phosphor (TSL).  During a de-trapping transition, free carriers created by the absorption of photons from the stimulating radiation field, recombine with the luminescence centers, whereby visible photons are emitted.  Since the OSL or TSL intensity is in the most cases proportional to absorbed dose of ionizing radiation, the phosphor materials which exhibit the OSL and TSL phenomena adapt to two-dimensional imaging sensor for ionizing radiation. 

Although imaging plate (IP) using photostimulable phosphor materials such as BaFBr:Eu [1,2] and CsBr:Eu [3] can be now used as two-dimensional sensor for ionizing radiation, these phosphor materials with deliquescent property exhibit poor fading characteristics which is one problem on two dimensional radiation dose estimation using the IP.  As a result of surveying many possible phosphor materials, we found that SnO-doped SrO-B2O3 and ZnO-P2O3 glass without deliquescent properties exhibit an efficient OSL and TSL, and good fading characteristics.  In this work, the OSL and TSL characteristics in x-ray irradiated SrO-B2O3 and ZnO-P2O3 glasses are in the first time reported.

Ref.

[1] K.Takahashi et al., J. Electrochemcal Soc., 32 (1985) 1492.

[2] M.Takebe and K.Abe, Nuclear Instruments and Methods, A345 (1994) 606.

[3]H.Nanto et al., Nuclear Instruments and Methods, A580 (2007)278.
Fabrication of Y2O3:Bi3+,Eu3+ Fluorescent Nanosheet Films By Electrophoretic Deposition
Authors: Kosuge Yuta , Iso Yoshiki , Isobe Tetsuhiko
Published: February 2020

Spectral down-shifters convert near-UV light, to which silicon solar cells typically have low sensitivity, to visible light that solar cells can convert to electric power. They can therefore improve the photoelectric conversion efficiency of the solar cells. Y2O3:Bi3+,Eu3+ nanosheets absorb near-UV light and emit red light. The nanosheets possess high photostability under the continuous near-UV excitation. In this study, we make efforts to fabricate Y2O3:Bi3+,Eu3+fluorescent nanosheet films on ITO-coated glass substrates by electrophoretic deposition.

 Bi(NO3)3･5H2O (0.004 mmol) was dissolved in ethylene glycol (2.6 mL). Y(NO3)3･6H2O (0.956 mmol) and Eu(NO3)3･6H2O (0.040 mmol) were dissolved in ultrapure water (30 mL). The aqueous solution was added to the ethylene glycol solution, and then the mixed solution was mixed with triethylamine (3 mL). The total volume of the suspension was adjusted to 40 mL by adding ultrapure water, and the resulting suspension was heated in an autoclave at 160 °C . After centrifugation and freeze-drying, the powdered product was heated to 600 °C and kept at that temperature for 2 h to obtain calcined sample. The calcined sample was mixed with an aqueous solution of trisodium citrate, and stirred for 2 h. Citrate-modified nanosheets were re-dispersed to an NaOH aqueous solution (pH=11). An aqueous emulsion of silicone-modified acrylic resin was added to the nanosheet suspension as a binder. A nanosheet film was fabricated on an ITO-coated glass substrate at the anode side by application of a constant voltage in the prepared suspension.

 The absolute values of zeta potentials of Y2O3: Bi3+,Eu3+ nanosheets dispersed in ultrapure water increased after modification with citrate ions. The increase in zeta potentials verifies that citrate ions act as a stabilizing agent to prevent aggregation of the nanosheets. The deposited film exhibited red luminescence under UV light. According to SEM observation, the film was composed of Y2O3: Bi3+,Eu3+ nanosheets and nanoparticles of silicone-modified acrylic resin.
Upconversion Emission from Li-Gd2O3 Phosphors Embedded into PS Films
Authors: Carmona-Tellez S. , Carro-Gastelum A. , Mariscal B. L. , Alarcon-Flores G. , Huerta Evelyn , Medina-Velazquez D. , Falcony Ciro
Published: February 2020

Dielectric materials doped with rare earth (RE3+) ions have received large attention due to their potential application in photonic devices. In particular, upconversion (UC) luminescence has been widely studied as a way to obtain visible light using lasers operating in the infrared region as excitation light. In general, in order to observe efficient UC emissions the host material should have low cutoff phonon frequency to allow for large lifetime decay of the RE ion excited electronic levels. In addition, UC efficiencies depend on the doping strategy used, for instance, using co-dopants as Yb and Li ions has been reported to increase the UC efficiency on Tm3+ doped materials.

In the present work, UC luminescence from Li-Gd2O3 phosphors doped with Tm3+ and Yb3+ and its incorporation into Polystyrene (PS) films are studied, under continuous wave excitation at 980 nm. Powder samples were prepared by simple evaporation technique. They were characterized using x-ray diffraction, SEM and and photoluminescet spectroscopy; a study of UC emission from Tm3+ ions as well as Yb3+ was performed. Yb3+ presence makes possible the thulium blue emission in the UC luminescence model, meanwhile lithium presence could increase the Tm light emissions due to a notable change into gadolinium oxide structure. Those phosphors were attached into PS films by spin coating technique, these films were characterized using IR spectroscopy, UV-Vis and AFM as well as SEM and photoluminescent spectroscopy. They have high transparency (close to 98%) and are also activated under continuous wave excitation at 980 nm.
Cathodoluminescence in Rare Earth Doped Perovskite Films for RGB Colors
Authors: Takashima Hiroshi , Nagao Masayoshi
Published: February 2020

We have studied PL and EL properties of chemically stable perovskite phosphor films. Pr-doped Ca0.6Sr0.4TiO3 perovskite films were grown epitaxially on SrTiO3 (001) substrates and their intense red luminescence were observed. The PL intensity was markedly increased by post-annealing treatments, and the maximum PL intensity was obtained by the combination of relatively low-temperature film growth at 600 °C and sequential rapid post-annealing at 1000 °C. 1 We have discovered perovskite thin film electroluminescence, opening a new optical application of regarding perovskite materials. Complete epitaxial growth of all of the layers and very flat interfaces with monoatomic steps have been obtained. With increasing driving voltage, the intensity of electroluminescence dramatically increases. The sharp electroluminescence peak at around 610 nm at 12 V becomes much stronger with increasing ac voltage. High-quality red color is produced and the working voltage for whole-surface electroluminescence is as low as 10 V. 2 The electron beam irradiation was a method of obtaining electrical and optically emitting. In this report, we show preparation of cathodoluminescence in perovskite films for RGB colors. The films were grown on double-side polished SrTiO3 (001) substrates by pulsed laser deposition. The single-phase polycrystalline targets were prepared by a conventional solid-state reaction method. Compositions of green, blue and red were [(Ca0
.
97Mg0
.
03)0
.
98Tb0
.
02]SnO3, Sr2(Sn0.95Ti0.05)O4 and Pr0.002(Ca0.6Sr0.4)0.997TiO3, respectively. During film growth, the SrTiO3 substrates were heated to 600 °C for film and the oxygen partial pressure was controlled at 50 Pa. An ArF excimer laser (λ = 193 nm) was used that had a repetition rate of 8 Hz and a fluence of around 1.2 J cm−2 pulse−1 at the target surface. In order to take out luminescence excited by the electron beam from the side opposite to with a film adhesion side, the both-side polished substrate which has about 70% (at 500nm) of transparent was used. The field emitter with a gate electrode was used for the source of electrons. The transmittance of film with both-side polished substrate after 1000°C post-annealing treatments was 67 % (at 500nm), indicating that the transmittance of the epitaxially grown alkaline-earth stannates film is very high. When the phosphor film of [(Ca0
.
97Mg0
.
03)0
.
98Tb0
.
02]SnO3was irradiated with the electron beam, the cathode luminescence peaks were observed at around 490, 543, 582, 620 nm. These results clearly show that CL has been successfully obtained in the perovskite films. By using thin film phosphor for FED, high resolution could be realized and it is efficient and also possibility of a long-life.

REFERENCES

(1) H. Takashima, et al,
Applied Physics Letters. 89 261915 (2006).

(2) H. Takashima, et al, Advanced Materials
.
21 3699 (2009)
Synthesis, Structure and Luminescence of Mn4+- Doped ATiO3 (A=Ca, Mg, Zn) Deep Red Phosphors
Authors: Medic Mina , Brik Mikhail G. , Srivastava Alok M , Djordjevic Vesna , Papan Jelena , Dramicanin Miroslav
Published: February 2020

Red emission of the Mn4+ ions incorporated in different materials is used in various applications, such as lighting and holographic recording. Mn4+ emission can improve color-rendering-index of phosphor-converted white-light-emitting diodes, and it is a promising candidate to replace the well-established rare-earth Eu activator in red phosphors.

Here, synthesis, structure, morphology, and detailed spectroscopic and crystal field analysis of Mn4+ doped metal titanates ATiO3 (A = Ca, Mg, Zn) are presented. Materials were prepared by combining sol-gel and molten salt methods. In the first step a typical sol-gel procedure is applied in which acetic acid, absolute ethanol, tetrabutyl titanate and metal compound were mixed at the molar ratio of 3:16:1:1 with appropriate amount of manganeze nitrate hexahydrate. In the second step, obtained dry gels were mixed with eutectic salt NaCl/KCl = 1:1 at molar ratio of 1:10, and then calcined at 750oC. Structural analysis was done by X-ray diffraction for all samples. Optical characterization included measurements of photoluminescence excitation and emission spectra, emission decay analyses and diffuse reflection measurements. Optical spectra showed emission and absorption bands originating from d–d electronic transitions (a d3 configuration). The energy levels of the Mn4+ ions in the crystal field of ATiO3 are calculated using the exchange charge model and showed nice matching with the experimental photoluminescence excitation and emission spectra.
(Invited) Red-Emitting Manganese-Doped Aluminum Nitride Phosphor
Authors: Cherepy Nerine , Payne Stephen , Harvey Nicholas , Aberg Daniel , Seeley Zachary , Holliday Kiel , Tran Ich , Zhou Fei , Martinez H. Paul , Demeyer Jessica , Drobshoff Alexander , Srivastava Alok M , Camardello Samuel , Comanzo Holly A , Schlagel Deborah , Lograsso Thomas
Published: February 2020

We report high efficiency luminescence with a manganese-doped aluminum nitride red-emitting phosphor under 254 nm excitation, as well as its excellent lumen maintenance in fluorescent lamp conditions, making it a candidate replacement for the widely deployed europium-doped yttria red phosphor. Solid-state reaction of aluminum nitride powders with manganese metal at 1900 °C, 10 atm N2 in a reducing environment results in nitrogen deficiency, as revealed by diffuse reflectance spectra. When these powders are subsequently annealed in flowing nitrogen at 1650 °C, higher nitrogen content is recovered, resulting in white powders. Silicon was added to samples as an oxygen getter to improve emission efficiency. NEXAFS spectra and DFT calculations indicate that the Mn dopant is divalent. From DFT calculations, the UV absorption band is proposed to be due to an aluminum vacancy coupled with oxygen impurity dopants, and Mn2+ is assumed to be closely associated with this site. In contrast with some previous reports, we find that the highest quantum efficiency with 254 nm excitation (Q.E. = 0.86±0.14) is obtained in aluminum nitride with a low manganese doping level of 0.06 mol%. The principal Mn2+ decay of 1.25 ms is assigned to non-interacting Mn sites, while additional components in the microsecond range appear with higher Mn doping, consistent with Mn clustering and resultant exchange coupling. Slower components are present in samples with low Mn doping, as well as strong afterglow, assigned to trapping on shallow traps followed by detrapping and subsequent trapping on Mn.

Figure 1
Simple Techniques to Improve the Measurement of Basic Optical Parameters in Luminescent Materials
Authors: Garcia-Santamaria Florencio , Setlur Anant A , Srivastava Alok M , Camardello Samuel , Murphy James , Sista Srinivas P , Comanzo Holly A , Addepalli Swarnagowri
Published: February 2020

Absorption and scattering coefficients are, together with quantum efficiency and spectral response, fundamental parameters that describe fluorescent phosphors and their behavior in white LEDs, fluorescent lamps and displays. Simple reflectance measurements typically performed in industry often confound the absorption and scattering coefficients and understanding their individual contributions can be challenging. In this talk we will describe techniques that allow, in a simple and precise manner, to measure accurately and independently the absorption and scattering coefficients relative to a reference sample.
(Invited) Non-Thermal Detrapping in Persistent Phosphors: Drawbacks and Opportunities
Authors: Smet Philippe F , Tydtgat Claude , Michels Simon , Kersemans Mathias , Poelman Dirk
Published: February 2020

Persistent phosphors, also called glow-in-the-dark materials, are a specific type of luminescent materials. They can emit light long after the excitation ended, which is realized by temporarily storing energy in the crystal lattice. Ambient heat can release the trapped charge carriers, after which recombination and light emission can occur.

For many applications, such as in emergency signage, the storage capacity of persistent phosphors should further be increased. This would open new application areas, such as glowing road marks [1]. We show that the excitation of the europium center in the blue emitting Sr2MgSi2O7:Eu,Dy by near-UV light not only leads to charge trapping – essential to the persistent luminescence - but also to optically stimulated release of previously trapped charges and subsequent luminescence (OSL) [2]. This is substantiated by specific charging-OSL experiments making use of the presence of a thermal barrier for trapping at low temperature. Furthermore, the optical detrapping is observed to be significantly more important when a larger fraction of the traps is already filled, suggesting OSL is the limiting factor in the storage capacity of persistent phosphors.

Not only photons can lead to detrapping, also pressure can in certain (mechanoluminescent (ML)) phosphors lead to light emission. Consequently, these materials can be used as pressure gauges or stress indicators [3]. Here we focus on the use of ML phosphors as a visualisation tool for ultrasound pressure fields [4]. In the case of BaSi2O2N2:Eu, a bluish green ML signal is observed proportional to the ultrasound intensity. An approach is presented to construct a 3D representation of the ultrasound pressure field. The obtained results are compared to numerical simulations, showing an excellent match [4].

[1] J. Botterman and P. F. Smet, "Persistent phosphor SrAl2O4:Eu,Dy in outdoor conditions: saved by the trap distribution," Opt. Express 23, A868-A881 (2015)

[2] C. Tydtgat et al., "Optically stimulated detrapping during charging of persistent phosphors," Opt. Mater. Express 6, 844-858 (2016).

[3] C.N. Xu et al., "Direct view of stress distribution in solid by mechanoluminescence, " Appl. Phys. Lett. 74, 2414-2416 (1999)

[4] M. Kersemans et al., "Fast reconstruction of a bounded ultrasonic beam using acoustically induced piezo-luminescence, " Appl. Phys. Lett. 107, 234102 (2015)
(Invited) Local Environment Analysis of Dilute Rare-Earth Dopants in Phosphor Materials
Authors: Yamamoto Tomoyuki
Published: February 2020

Doping technique, i.e., incorporation of dilute amount of additional element, has been widely applied to add new functions for various kinds of materials. Appropriate doping can change their specific properties significantly, e.g., electric, magnetic, optical, mechanical and chemical properties, etc. It is, of course, fundamental to know the crystal and electronic structures of such materials. In addition to such studies, it is mandatory to investigate the local environment of dopants on an atomic scale to understand the mechanism of appearance of new properties by doping and to design new materials with desired properties by such doping technique. Although crystal structure analysis has been widely carried out by the X-ray diffraction (XRD) technique, it is very difficult to determine the local environment of dilute dopants only by XRD. There are some experimental methods to investigate such local environment of dilute dopants. Among these methods, X-ray absorption near-edge structure (XANES) analysis by using the synchrotron radiations is one of the most powerful methods, which enables us to determine the local environment of dopant at an ultra-dilute concentration level, such as atomic ppm level of concentration [1]. We have reported quantitative analysis of XANES from many different kinds of functional materials [2, 3] with the aid of the first-principles calculations within the density functional theory (DFT). The fingerprint type analysis is widely accepted for various kinds of analysis, but such strategy requires reliable fingerprints to be compared with the newly observed result. However, in the case of local environment analysis by XANES, observed XANES spectrum from dopant often shows different profile from any of the standard ones, which yields that fingerprint type of analysis does not work for the local environment analysis. From such reason, theoretical fingerprint prepared by using first-principles calculation plays a key role for the local environment analysis of dopant by XANES.

In the current study, we focus upon local environment analysis of dilute dopants in phosphor materials. After introduction of our analytical method of the local environment analysis with XANES and first-principles calculation, several results on such dopants, rare-earth ions and 3d-transition metal ions in perovskite structured oxides, will be shown. As an example, Ga XANES analysis of Ga doped SrTiO3:Pr, in which Ga codoping enhances red luminescence of Pr doped SrTiO3 [3], is shown in Fig. 1.

References

[1] I. Tanaka et al., Nature Materials 2 (2003) 541.

[2] I. Tanaka et al., J Am. Cer. Soc. 88 (2005) 2013.

[3] T. Yamamoto et al., J. Phys.: Condens. Matter 21 (2009) 104211.

Figure 1
Dependence of Optical Properties of Mn4+ on Temperature and Chemical Environment in A
2Ge4O9 (A = K, Rb)
Authors: Baur Florian , Juestel Thomas
Published: February 2020

The optical properties of the novel red-emitting A
2Ge4O9:Mn4+ (A = K, Rb) phosphors exhibit an unusually strong dependence on temperature. The dependence of Racah parameters B and C as well as crystal field factor Dq was determined. It was found that C exhibits an inverse trend in regard to B. This observation was linked to a potential change in bond angles of the Mn4+ dopant site. Mn4+ occupies two sites in the material, causing a double Fermi-Dirac quenching behavior. Mn4+ on the site with larger Mn-O distances shows a lower thermal quenching temperature. Decay constants were calculated from temperature dependent decay measurements. The constants decrease steadily with temperature, most likely not due to thermal quenching but an increase of the 2Eà4A2 transition probability.
Light Extraction Enhancement in GaN-Based Light-Emitting Diodes with Patterned Micro-Pillars
Authors: Kwon Heera , Kim Hyunsoo , Cho Jaehee
Published: February 2020

A nitride-based light-emitting diode (LED) is a key device for the next-generation solid-state lighting due to its high efficiency, high reliability, and potential to offer new functionalities. However, the large contrast in the refractive index between the LED semiconductor and ambient air (i) limits the light extraction efficiency (LEE) of LEDs by means of total internal reflection, and (ii) distorts the spatial distribution of light intensity emitted from the LED. As a result, planar-surface LEDs normally have a very low LEE and an emission pattern with the peak emission intensity along the LED surface-normal. Such a pointed emission pattern is not appropriate for uniform illumination, e.g. an interior and a street lighting.

These two problems have been solved separately. First, the low LEE of GaN-based LEDs has been improved by means of surface/interface roughening and chip shaping. Second, the emission pattern of LEDs has been controlled by the help of secondly optics and external cavities such as photonic crystals. However, a combined solution for both problems requires advanced manipulation capabilities for the surface of LEDs, which is not fully developed yet.

Here, we present a technique that provides full control of surface properties (esp. refractive index) in the LED structure: the LEDs having patterned micro-pillars. The effect of the patterned micro-pillars is investigated and the structure of micro-pillars is optimized in order to obtain maximum LEE and also emission-pattern control.
Tunable Eu2+ Emission in KxNa1-XLuS2 Phosphors for Circadian LEDs
Authors: Jary Vitezslav , Havlak Lubomir , Barta Jan , Buryi Maksym , Rejman Martin , Laguta Valentin , Nikl Martin
Published: February 2020

Set of novel Eu2+-doped KxNa1-xLuS2 phosphors (where x = 0 – 1) was successfully synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, X-ray excited fluorescence, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Special attention is given to photoluminescence emission spectra under the 395 nm and 455 nm excitation aiming to obtain white emission with tunable color temperature, which is desirable for circadian white LEDs construction. EPR method is employed to understand the Eu2+ incorporation and distribution in the KxNa1-xLuS2 hosts. CIE xy-coordinates are used to compare effects of different K/Na concentration in KxNa1-xLuS2 on resulting spectrum (Figure 1). The application potential of mentioned compounds in the field of white LED solid state lighting phosphors with tunable color temperature is thoroughly discussed. The realistic circadian light bulb is presented as well and its properties are addressed.

Figure 1
A Single Phase LaAl(Si6-zAlz)(N10-zOz):Eu2+ Phosphor with Large Red-Shift of the Emission and Anomalous Decay Behavior
Authors: Wang Chunyun , Takeda Takashi , ten Kate Otmar Melvin , Funahashi Shiro , Tansho Masatako , Takahashi Kohsei , Xie Rong-Jun , Shimizu Tadashi , Hirosaki Naoto
Published: February 2020

Phosphor-converted light-emitting diodes (pc-LEDs) have penetrated to solid-state lighting over the last decades because of high energy conversion efficiency, long lifetime and environmental benefits. White pc-LEDs with high luminous efficacy and color rendition are urgently required, especially for illumination-grade light sources. Ce doped LaAl(Si6-zAlz)(N10-zOz) (termed JEM) phosphor has been reported as a promising phosphor for white LEDs using near UV excitation, particularly for home illumination.1 However, the unavailability of a phase pure JEM:Ce phosphor prevents widespread application and detailed crystal structure analysis. In addition, Eu2+ and Ce3+ are the most effective activators for white LED phosphors, but there is no report on the photoluminescence properties of an Eu2+doped JEM phosphor.

In the present study, a phase pure Eu2+ doped JEM phosphor and non-doped JEM were successfully obtained with a solid-state reaction method by carefully controlling the synthesis temperature and chemical composition of starting materials. The Eu2+ doped JEM phosphors show a very interesting red-shift of the emission band; the emission color after excitation with 355 nm light can be tuned from blue-green to yellow by increasing the Eu concentration. Furthermore, an anomalous decay behavior with bi-exponential decay was observed, although there is only one crystallographic site in the JEM structure. 2With the single phase JEM sample achieved, we investigated the details of the crystal structure by XRD and magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR).

Reference

1. K. Takahashi, N. Hirosaki, R.-J. Xie, M. Harada, K. Yoshimura and Y. Tomomura, Appl. Phys. Lett. 91, 091923 (2007).

2. J. Grins, Z. Shen, M. Nygren and T. Ekström, J. Mater. Chem. 5, 2001 (1995).

Fig1. A scheme of the large red-shift emission (a) and anomalous decay behavior (b) for JEM:Eu2+ phosphor and JEM crystal structure (c).

Figure 1
(Invited) White LEDs Using Oxynitride Green Phosphor and Mn-Doped Red Phosphor for Wide-Color Gamut Display Applications
Authors: Yoshimura Kenichi , Fukunaga Hiroshi , Izumi Makoto , Masuda Masatsugu , Uemura Toyonori , Takahashi Kohsei , Xie Rong-Jun , Hirosaki Naoto
Published: February 2020

β-sialon (Si6-zAlzOzN8-z):Eu oxynitride phosphor is suitable to be used as a green phosphor for the wide-color gamut white LEDs backlighting system, when combined with a blue LED chip and CaAlSiN3:Eu red phosphor, because of its sharp and asymmetric emission spectrum shape.[1, 2] The display color gamut can be widened by the utilization of β-sialon:Eu because its emission spectrum is blue shifted and width of the emission spectrum is narrowed with decreasing z value down to less than 0.1. [3] β-sialon:Eu with low z values of less than 0.1 hereinafter referred to “sharp β-sialon:Eu”. However, the color gamut of the display with sharp β-sialon:Eu and CaAlSiN3:Eu is restricted due to the large full-width at half maximum of the emission spectrum of CaAlSiN3:Eu (> 90 nm).In this work, we attempted to use the K2SiF6:Mn phosphor as an alternative red phosphor which has a sharp emission spectrum, and a sharp β-sialon:Eu as the green phosphor, for the purpose of improving the display color gamut and brightness.

White LEDs were fabricated by combining a InGaN blue LED chip peaked at 445nm and sharp β-sialon:Eu (z=0.05) as a green phosphor and K2SiF6:Mn or CaAlSiN3:Eu as a red phosphor. Figure 1 shows emission spectra of fabricated white LEDs and the transmittance spectra of RGB filter are also shown in Fig. 1. Table I shows the color gamut and the brightness of the displays using the white LEDs as the backlight devices. The display using K2SiF6:Mn showed wider NTSC ratios and higher brightness compared to that using CaAlSiN3:Eu. The superiority of the display using K2SiF6:Mn shown in Table I was mainly attributed to the very narrow emission spectrum of the red phosphor. Moreover, the color gamut of the display with the sharp β-sialon:Eu phosphor and K2SiF6:Mn phosphor was mostly able to cover the NTSC triangles as shown in Fig. 2.

[1] N. Hirosaki, R-J. Xie, K. Kimoto, T. Sekiguchi, Y. Yamamoto, T. Suehiro, and M. Mitomo, Appl.Phys.Lett. 86, 211905 (2005).

[2] R.-J. Xie, N. Hirosaki, and T. Takeda, Appl. Phys. Express. 2, 200401 (2009).

[3] K. Takahashi, K. Yoshimura, M. Harada, Y. Tomomura, T. Takeda, R.-J. Xie, and N. Hirosaki, Sci. Adv. Mater. 13, 015004 (2012).

Figure 1
Synthesis, Crystal Structure and Optical Spectroscopy of Eu2+ in Sr3SiO4Br2, Along with Potential Applications in LEDs
Authors: Camardello Sam Jospeh , Srivastava Alok M , Her Jae-Hyuk , Setlur Anant A
Published: February 2020

In the ternary phase system, SrO-SiO2-SrBr2, a new material was identified which upon Eu2+ activation resulted in red emission that is useful for LED applications. In this talk, we will discuss the single crystal growth, and the optical properties of Eu2+ in Sr3SiO4Br2. The relevant parameters for use in LED applications such as thermal dependence of emission, QE and excitation are measured and reported. The effects of cationic substitutions of Ca2+ and Ge4+ on the luminescent properties of the Eu2+ ion in Sr3SiO4Br2 will also be described.

Figure 1: Single crystals of Sr3SiO4Br2 and Sr3GeO4Br2 under daylight and UV excitation along with the emission spectra.

Figure 1
Bioelectronically Initiated Cyt P450s Catalysis without NADPH
Authors: Liu Songqin , Xu Xuan
Published: February 2020

The catalytic cycle of cytochrome P450s (cyt P450s) features delivery of electrons from NADPH to cyt P450 reductase (CPR) for subsequent delivery to cyt P450 heme. Attempts at bioelectronic initiation of cyt P450s catalysis have been made by replacing the electron donation from expensive NADPH by other electron donnors. 1

To this aim, an electrode-driven drug metabolism biosensors were constructed with a mixed film containing ITO nanoparticles and CYP2C9/CPR-microsomes encapsulated by chitosan (CS) on a GC electrode. The electrochemical response of the enzyme modified electrode to 4-hydroxylation of tolbutamide has been validated, which allowed rapid determination of the affinity parameter Km
appat 202.84 μM. The inhibition effect of sulfaphenazole on the CYP2C9-dependent 4-hydroxylation of tolbutamide was also investigated.

Quantum dots (QDs), a kind of semiconductor materials, can also act as electron donnors. Based on the photo-induced electron transfer (PET) from QDs to the hemoproteins, a photoelectrochemical biosensor for the light-controlled drug metabolism by cyt P450s was then constructed. As shown in scheme 1, the photosensitized QDs offer electrons demanded in the cyt P450 catalytic process while the electrode at appropriate bias potentials acts as an electron supplier to QDs for neutralizing the VB holes and monitors the occurrence of the light-induced catalytic process. This novel biosensor can be applied in drug discovery and development by monitoring substrate metabolism and enzyme inhibition.

 

References

 [1] (a) N. Bistolas, U. Wollenbergera, C. Jung and F. W. Scheller, Biosens. Bioelectron., 2005, 20, 2408–2423; (b) S. Krishnan, J. B. Schenkman and J. F. Rusling, J. Phys. Chem. B, 2011, 115, 8371–8380.
Electrochemically Switchable Fluorescence in Rhodamine Derivatives
Authors: Cizkova Martina , Cattiaux Laurent , Mallet Jean-Maurice , Amatore Christian Andre , Labbe Eric , Buriez Olivier
Published: February 2020

Monitoring therapeutic-agent translocation to the cell interior represents one of the significant problems in drug development. Carrier-mediated transport across cellular membranes is frequently executed by fluorophore-labelled cell-penetrating peptides (CPPs),[1] and the process is routinely studied with fluorescence microscopy. Nevertheless, since fluorescence cannot discriminate membrane-bound and bulk-solution peptides in the internal compartment, misleading false positive results may be introduced into the interpretation of translocation processes.[2] Also, classical fluorescent probes currently used are not reversibly switchable. In this context, the development of electrochemically switchable fluorescent probes is of high interest.[3] Therefore, we designed original rhodamine derivative and investigated its spectroelectrochemical properties (Figure 1), which were compared with spectroelectrochemical properties of a commercially available analogue rhodamine 101. The combination of cyclic voltammetry and UV-Vis absorbance and fluorescence spectroelectrochemical experiments showed that the starting fluorescent cationic rhodamine derivatives can be reversibly reduced into the corresponding non-fluorescent radical compounds. Importantly, the stability of electrogenerated radical species allowed reversible activation/deactivation of fluorescence as a function of time and potential values.

Figure 1. a) Reversible electrochemical reduction of the new rhodamine derivative. b) UV-Vis spectra of the original cationic compound and species formed after the first and second reduction. c) Electrochemically mediated fluorescence decrease.

 

Acknowledgement

The financial support from the EU Research and Innovation programme Horizon 2020
through the Marie Skłodowska-Curie action (H2020-MSCA-IF-2014, ID 656519) is gratefully acknowledged

References

[1] a) Frankel, A. D.; Pabo, C.O. Cell 1988, 55, 1189; b) Järver, P.; Langel, Ü. Biochim. Biophys. Act. 2006, 1758, 260; c) Trabulo, S.; Cardoso, A. L.; Mano, M.; Pedroso de Lima, M. C. Pharmaceuticals 2010, 3, 961; d) Dietz, G. P. H.; Bahr, M. Mol. Cell. Neurosci. 2004, 27, 85.

[2] Richard, J. P.; Meliko, K.; Vives, E.; Ramos, C.; Verbeure, B.; Gait, M. J.; Chernomordik, L. V.; Lebleu, B. J. Biol. Chem. 2003, 278, 585.

[3] Audebert, P.; Miomandre, F. Chem. Sci. 2013, 4, 575.

Figure 1
Demonstration of an Energy Neutral, Off-Grid Microbial Fuel Cell System for Decentralized Wastewater Treatment
Authors: Hsu Lewis , Arias-Thode Meriah , Bretschger Orianna , Salvacion Michael , Chen Shing , Benavidez Zach , Babanova Sofia
Published: February 2020

Water and energy are main priorities for much of the world as increasing demands on the world’s resources forces nations to make sustainable choices. Microbial fuel cells emerged as a promising technology to provide energy efficient wastewater treatment at significant cost savings compared to conventional treatment processes. They have an even greater benefit in those areas that are difficult to connect to municipal sewage treatment networks.

We discuss here a pilot scale demonstration at a rural Naval training camp in Warner Springs, CA. The system is a 100 gallon system outfitted with a solar energy system that allows full system operation in an energy neutral configuration. The system configuration here was previously tested in the laboratory using wastewater in semi-batch operation at both the 40 gallon scale and 100 gallon scale. Laboratory studies indicated that a 7-day batch treatment time would result in high removal of biological oxygen demand. Effluent quality was also good with more than 99% removal of suspended solids, turbidity, and nitrogen.

Before deployment to the field, the system was rebuilt using lessons learned from the laboratory studies and other large scale demonstrations. Considerations for size, portability, ease of use, and operations were considered here and will be discussed. The overall goal for the field-deployed system was to demonstrate continuous treatment at rate of 20 gallon per day. Initial results from the startup phase operating in semi-batch mode show promising results, decreasing the COD content more than 80% over a 7-day treatment time. Results from the ongoing demonstration will also be discussed here.

The system here represents a significant move towards providing decentralized wastewater treatment. We examine the feasibility of applying this technology in an off-grid application to meet a real-world requirement. We will also examine lessons learned from the demonstration and possible improvements to incorporate into the next iterations of these types of systems.
Designing Macro-Meso Pore Structure of MgO-Templated Carbon for Det-Based Enzyme Electrodes
Authors: Funabashi Hiroto , Tsujimura Seiya
Published: February 2020

Porous carbon materials, including carbon nanotubes and carbon blacks, and mesoporous carbons, carbon cryogel and carbon aerogel, have attracted attention for improving the performance of enzymatic electrode. Carbon nanotubes and carbon blacks aggregate and create mesospaces suitable for enzymatic reactions. However, much of the mesospaces is unused because the pore size is random and controlling the pore structure and pore size is difficult. In contrast, carbon cryogel or aerogel has a well-controlled mesopore size distribution with an average pore diameter ranging from 10 to 100 nm. However, the procedure of carbon gel production is time-consuming and not suitable for mass production. We focused on a new mesoporous carbon material, MgO-templated carbon (MgOC) as an alternative to carbon gels. The mesopore size can be controlled by alternating the MgO template size[1]. One of the striking advantages of MgOC over the previously reported mesoporous carbons is its simple and cost-effective production procedure.

The effects of the pore structure of MgOCs on the direct electron transfer (DET) reaction of redox enzyme, D-fructose dehydrogenase, and bilirubin oxidase, were investigated[2]. We found two effects of optimizing pore structure. First, the macropores of MgOC can enhance current production. When the pore size of MgOC was much larger than the size of enzyme, the MgOC could adsorb a sufficient amount of enzyme even on the pores formed inside the MgOC particle structure, and the enzymes adsorbed inside the MgOC worked well as an electrocatalyst. In contrast, when the pore size of MgOC was comparable to the size of enzymes, the enzymes could not penetrate the MgOC particles through the inter-connecting pores, and only the enzyme adsorbed on the mesopores formed at the surface of the carbon particles produced catalytic current. Second, the mesopores which were close to the size of enzymes improve thermal stability of electrode. When enzymes molecules were embedded in the carbon mesopores with pore size comparable to that of enzymes, an enhanced contact area between enzymes and the MgOC surface led to strong adsorption of enzymes on the MgOC surface as well as to enzyme stabilization by preventing the denaturation, aggregation and collision of enzyme molecules. Furthermore, we developed the novel MgOC which have hierarchical structure composed by meso-macro pores. This material improved current density and thermal stability of enzyme modified electrodes.

Reference

[1] T. Morishita, T. Tsumura, M. Toyoda, J. Przepiórski, A. W. Morawski, H. Kanno,

and M. Inagaki, Carbon, 48, 2690 (2010)

[2] H. Funabashi, K. Murata, S. Tsujimura,

Electrochemistry, 83(5), 372 (2015).
Synthesis and Electrochemical Properties of Thiophene-Based Polymers As Organic Cathode Materials for Lithium-Ion Batteries
Authors: Tanizawa Hideya , Shimizu Akihiro , Yaso Yusuke , Inatomi Yuu , Hojo Nobuhiko , Suzuki Hirotetsu , Yoshida Jun-ichi
Published: February 2020

Organic rechargeable batteries have received significant research interest in terms of structural diversity, flexibility, and sustainability of organic active materials. We have previously reported that polymethacrylate-bound pyrene-4,5,9,10-tetraone (PYT) serves as an excellent cathode material. However, the search for better polymer structures is still required to develop better cathode materials.

Herein we report thiophene-based polymers, poly[(thiophene)-alt-(PYT)] (PTPYT, 1) and Poly[3-(dioxodihydroquinoxalinyl)thiophen-2,5-diyl] (2). As a core structures we chose not only PYT but also quinoxaline-5,8-dione (QD) because QD has high theoretical capacity of 335 mAh/g and high discharge voltage of 2.8 V vs. Li/Li+. The charge–discharge behavior of the polymers 1 and 2 was studied using a coin-type cell using LiPF6/propylene carbonate (LiPF6/PC) or LiN(SO2CF3)2/dimethoxy ethane (LiTFSI/DME) as electrolytes. The battery composed of 1 and that composed of 2 exhibited reversible discharge–charge behavior with average discharge voltages of ca. 2.4 and 2.8 V vs. Li/Li+, respectively. The batteries exhibited good cyclability and after 20 charge–discharge cycles, they retained 65% - 85% of the initial capacity.Organic rechargeable batteries have received significant research interest in terms of structural diversity, flexibility, and sustainability of organic active materials. We have previously reported that polymethacrylate-bound pyrene-4,5,9,10-tetraone (PYT) serves as an excellent cathode material. However, the search for better polymer structures is still required to develop better cathode materials.

Herein we report thiophene-based polymers, poly[(thiophene)-alt-(PYT)] (PTPYT, 1) and Poly[3-(dioxodihydroquinoxalinyl)thiophen-2,5-diyl] (2). As a core structures we chose not only PYT but also quinoxaline-5,8-dione (QD) because QD has high theoretical capacity of 335 mAh/g and high discharge voltage of 2.8 V vs. Li/Li+. The charge–discharge behavior of the polymers 1 and 2 was studied using a coin-type cell using LiPF6/propylene carbonate (LiPF6/PC) or LiN(SO2CF3)2/dimethoxy ethane (LiTFSI/DME) as electrolytes. The battery composed of 1 and that composed of 2 exhibited reversible discharge–charge behavior with average discharge voltages of ca. 2.4 and 2.8 V vs. Li/Li+, respectively. The batteries exhibited good cyclability and after 20 charge–discharge cycles, they retained 65% - 85% of the initial capacity.
Hole Transfer Property at Single Crystal Prepared from Triphenylamine-Derivative Based on Solubility and Supersolubility Curves
Authors: Nakasone Yasuaki , Shironita Sayoko , Nagayama Norio , Umeda Minoru
Published: February 2020

In this report, we describe anisotropic hole transport in a triphenylamine-derivative single crystal prepared by a solution method with solubility and supersolubility curves. Triphenylamine derivatives are commonly used as a hole-transport material for organic devices. In the electrophotographic photoconductors, the materials are used in an amorphous form, in which charge carrier mobility is in the order of ~104 cm2V-1s-1. For realizing a further high mobility as an organic semiconductor, preparation of a single crystal seems to be a promissing way. In this study, a single crystal of a trihenylamine derivative (TPA : α-Phenyl-4'-[(4-methoxyphenyl)phenylamino]stilbene) was prepared and its anisotropic hole transport property was measured.

Firstly, solubility and supersolubility curves were measured employing a tetrahydrofuran (THF) as a solvent. Based on the results, a single crystal preparation was conducted using 45 wt.% TPA solution with a cooling rate of 0.125 °Ch-1 started from 35°C for 48 h, resulted in a crystal of 8 x 0.8 x 0.4 mm. A polarizing microscope observation demonstrated an extinction angle, which ensures that the TPA single crystal is obtained.

Next, current-voltage properties of the TPA single crystal were measured in a vacuum chamber connected to a source meter (Keythley 2612A). For the measurement, A set of Au parallel electrodes with a distance of 20 μm were vacuum deposited on the crystal. From the results, long-axis (direction of 8 mm at TPA single crystal) current is larger than the short-axis (direction of 0.8 mm at TPA single crystal) current, which reveals anisotropic hole transport in the crystal is observed. This can be well explained by a molecular orientation of the crystal structure.

Figure 1
Innovation of New Luciferin Analog for In Vivo Imaging
Authors: Saito Ryohei , Kiyama Masahiro , Kitada Nobuo , Higashi Shoko , Iwano Satoshi , Obata Rika , Niwa Haruki , Hirano Takashi , Maki Shojiro
Published: February 2020

【Introduction】

We are innovating new imaging technologies by using organic chemistry. For making advanced medicinal technology, in vivo imaging is needed. So, we have been developing compounds suitable for deep in vivo imaging.

【Background】

It is very difficult for deep in vivo imaging to be absorbed and scattered light in living tissue. But, it is well known that the light in the near infrared region (NIR) has high permeability for the living tissue. It is a challenge to visualize in vivo deep imaging by developing an imaging material that has NIR emission. We have got structure-activity relationship data on the firefly luciferin luciferase reaction. According to the structure-activity relationship data on luciferin analogues, we have designed and marked NIR probe “AkalumineⓇ, (WAKO pure chemical LTD.). AkalumineⓇ gives a higher brightness compared with the natural firefly luciferin because of high permeability AkalumineⓇ in tissue.

【Purpose】

We try to rise concentration of the firefly luciferin for high dose. But we faced difficulty that AkalumineⓇ has low water-soluble.

For various applications, “high dose” is key technology on in vivo imaging.

Based on the AkalumineⓇstructure, new luciferin analogues have designed and synthesized three types.

【Result and conclusion】

We made the substances of three new luciferin analogues. One of these emits in the NIR and another has water-solubility increased by 15 fold for AkalumineⓇ.

We will apply new probe to the animal for conforming practical ability and discuss these new luciferin analogues for in vivo imaging technology.
Biological Decontamination of Water Using Non-Thermal Plasma Treatment
Authors: Abdel-Fattah Tarek M , Cetinkaya Ekrem , Pell William , Malik Muhammad
Published: February 2020

The field of biological decontamination of water using non-thermal plasma formation is a novel and rapidly growing field due to its importance for environmental sustainability. The current method of decontaminating water is by adding chemicals that destroy harmful bacteria and viral pathogens. However, this has the risk of forming chemical byproducts that could also be harmful to humans. The way non-thermal plasma works is by ionizing gas and water molecules under pulsed electric fields. It results in shockwaves, reactive species like hydroxyl radicals, atomic oxygen and ozone; all of which aid in effectively killing the bacteria, rendering the water safe to drink and free of harmful byproducts. The plasma is generated in a reaction chamber by applying pulsed high voltage pulses of nano-second duration across two parallel strip electrodes.

E. coligrown in Luria’s Broth was inoculated in to sterilized water which ran through the plasma chamber at 1 mL per minute. The obtained water was diluted and plated on agar plates. A control was conducted in order to study the effect of plasma. The obtained plates were incubated and the colony forming units (CFUs) were counted after incubation. The results obtained showed a 65% decrease from 244 CFUs to 89 CFUs significantly reducing the bacterial count from the control.

The significance of an alternative decontamination method, both cost effective and safe will be an answer to the increasing scarcity of clean water all around the world. This method will especially be useful in developing countries.

References:

1) Anpilov, A., Barkhudarov, E., Christofi, N., Kop'ev, V., Kossyi, I., Taktakishvili, M., and Zadiraka, Y. Pulsed high voltage electric discharge disinfection of microbially contaminated liquids.
2002, Letters in Applied Microbiology, 35(1), 90-94.

2) Barkhudarov, E. M., Kossyi, I. A., Kozlov, Y. N., Temchin, S. M., Taktakishvili, M. I., and Christofi, N. Multispark discharge in water as a method of environmental sustainability problems solution. 2013, Journal of Atomic and Molecular Physics,

3) Malik M. A., Ghaffar A. and Malik S. A. 2001, Plasma Sources Sci. Technol. 10 82–91