Enhanced Photoluminescence Emission and Thermal Stability from Introduced Cation Disorder in Phosphors

Optimizing properties of phosphors for use in white-light-emitting diodes (WLEDs) is an important materials challenge. Most phosphors have a low level of lattice disorder due to mismatch between the host and activator cations. Here we show that deliberate introduction of high levels of cation disorder leads to significant improvements in quantum efficiency, stability to thermal quenching, and emission lifetime in Sr_{1.98–<i>x</i>}(Ca_0.55Ba_0.45)_<i>x</i>Si₅N₈:Eu_0.02 (<i>x</i> = 0–1.5) phosphors. Replacing Sr by a (Ca_0.55Ba_0.45) mixture with the same average radius increases cation size variance, resulting in photoluminescence emission increases of 20–26% for the <i>x</i> = 1.5 sample relative to the <i>x</i> = 0 parent across the 25–200 °C range that spans WLED working temperatures. Cation disorder suppresses nonradiative processes through disruption of lattice vibrations and creates deep traps that release electrons to compensate for thermal quenching. Introduction of high levels of cation disorder may thus be a very useful general approach for improving the efficiency of luminescent materials

Aluminate red phosphor in light-emitting diodes : theoretical calculations, charge varieties and high-pressure luminescence analysis

This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104-2113-M- 002-012-MY3 and MOST 104-2923-M-002-007-MY3). This research was also supported by National Centre for Re- search and Development, Poland (Grant No. PL- TW2/8/2015).Searching for a non-rare earth-based oxide red-emitting phosphor is crucial for phosphor-converted light- emitting diodes (LEDs). In this study, we optimized a blue and UV-light excited Sr4Al14O25:Mn phosphor exhibiting red emission peaked at ~653 nm, which was successfully synthesized by solid-state reaction. The crystal structure, micromorphology, and luminescent properties of Sr4Al14O25:Mn phosphors were characterized by X-ray Rietveld refinement, high-resolution transmission electron microscopy, and photoluminescence spectra. The band gap and electronic structure of Sr4Al14O25 were analyzed by density functional theory calculation using the hybrid exchange- correlation functional. The crystal field environment effect of Al sites from introducing activator Mn ions was investigated with the aid of Raman 27Al nuclear magnetic resonance spectra and electron spin resonance. The pressure dependent on the luminescent properties and decay time of this compound were presented. The tricolor display spectrum by combining blue InGaN chips, commercial β-SiAlON:Eu2+ green phosphor, and Sr4Al14O25:Mn red phosphor were evaluated for commercial applications: using the present Sr4Al14O25:Mn red phosphor converted LED as backlighting source.PostprintPeer reviewe

Control of luminescence by tuning of crystal symmetry and local structure in Mn4+-activated narrow band fluoride phosphors

This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104-2113-M-002-012-MY3 and MOST 104-2923-M-002-007-MY3) and National Center for Research and Development Poland Grant (No. PL-TW2/8/2015). Y Jin thanks the National Nature Science Foundation of China (No. 11104366), Chongqing Research Program of Basic Research and Frontier Technology (No. cstc2014jcyjA50018), and the Scientific and Technological Research Program of Chongqing Municipal Education Commission (No. KJ1500913). T. Lesniewski would like to acknowledge the support of University of Gdansk Research Grant 538-5200-B468-17.Mn4+-doped fluoride phosphors have been widely used in wide-gamut backlighting devices because of their extremely narrow emission band. In this study, solid solutions of Na2(SixGe1-x)F6:Mn4+ and Na2(GeyTigros)F6:Mn4+ have been successfully synthesized to elucidate the behavior of zero-phonon line (ZPL) in different structures because of the sensitivity of ZPL intensity to the local coordinated environment. The structures of the products are examined by X-ray diffraction and Rietveld refinement. The ratio between ZPL and the highest emission intensity υ6 phonon sideband exhibits a strong relationship with luminescent decay rate. First-principles calculations are conducted to model the variation in the structural and electronic properties of the prepared solid solutions as a function of the composition. The calculated results are consistent with the experimentally determined structural parameters. To compensate for the limitations of Rietveld refinement, electron paramagnetic resonance and high-resolution steady-state emission spectra are used to prove the diverse local environment for Mn4+ in the structure. Finally, the spectral luminous efficacy of radiation (LER) is used to reveal the important role of ZPL in practical application.PostprintPeer reviewe

Controlling of structural ordering and rigidity of β-SiAlON:Eu through chemical cosubstitution to approach narrow-band-emission for light-emitting diodes application

The authors are grateful for the financial support of the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 104- 2113-M-002-012-MY3, MOST 104-2119-M-002-027-MY3 and 104-2923-M-002-007-MY3) and Australia Research Council (ARC, FT160100251). The contribution of A. L. was supported by the grant “Preludium” UMO-2014/13/N/ST3/03781 from the National Science Center. The contribution of S. M. was supported by the grant “Iuventus Plus” 0271/IP3/2015/73 from the Ministry of Science and Higher Education. M. G. was supported by Polish National Center for Research and Development with grants no PBS3/A5/48/2015 and PL-TWII/8/2015.Narrow-band green-emitting phosphor β-SiAlON:Eu has been widely used in advanced wide-gamut backlighting de- vices. However, the origins for unusual sharp lines in photoluminescence emission at room temperature and tunable narrow-band- emission tailored by reducing Al-O in β-SiAlON:Eu are still unclear. Here, the presence of sharp-line fine structure in the emission spectra of β-SiAlON:Eu is mainly due to purely electronic transitions (zero phonon lines) and their vibronic repetitions resulted from the multi-microenvironment around Eu2+ ions that has been revealed by relative emission intensity of sharp line depends on excitation wavelength and monotonously increasing decay time. The specific features of the Eu2+ occupying interstitial sites indicate that the effect of crystal field strength can be neglected. Therefore the enhanced rigidity and higher ordering structure of β-SiAlON:Eu with decreasing the substitution of Si–N by Al–O become the main factors in decreasing electron–lattice coupling and reducing inhomo- geneous broadening, favouring the blue-shift and narrow of the emission band, the enhanced thermal stability, as well as the charge state of Eu2+. Our results provide new insights for explaining the reason for narrow-band-emission in β-SiAlON:Eu, which will deliver an impetus for the exploration of phosphors with narrow band and ordering structure.PostprintPeer reviewe

Simple sequence repeat-based consensus linkage map of \u3cem\u3eBombyx mori\u3c/em\u3e

We established a genetic linkage map employing 518 simple sequence repeat (SSR, or microsatellite) markers for Bombyx mori (silkworm), the economically and culturally important lepidopteran insect, as part of an international genomics program. A survey of six representative silkworm strains using 2,500 (CA)n- and (CT)n-based SSR markers revealed 17-24% polymorphism, indicating a high degree of homozygosity resulting from a long history of inbreeding. Twenty-nine SSR linkage groups were established in well characterized Dazao and C108 strains based on genotyping of 189 backcross progeny derived from an F1 male mated with a C108 female. The clustering was further focused to 28 groups by genotyping 22 backcross progeny derived from an F1 female mated with a C108 male. This set of SSR linkage groups was further assigned to the 28 chromosomes (established linkage groups) of silkworm aided by visible mutations and cleaved amplified polymorphic sequence markers developed from previously mapped genes, cDNA sequences, and cloned random amplified polymorphic DNAs. By integrating a visible mutation p (plain, larval marking) and 29 well conserved genes of insects onto this SSR-based linkage map, a second generation consensus silkworm genetic map with a range of 7-40 markers per linkage group and a total map length of ≈3431.9 cM was constructed and its high efficiency for genotyping and potential application for synteny studies of Lepidoptera and other insects was demonstrated

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake