bluuebunny/crossref_metadata_2025_split huggingface dataset:
(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
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.
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).