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News Article | December 28, 2016
Site: www.eurekalert.org

Reproducibility is a necessity for science but has often eluded researchers studying the lifetime of organic light-emitting diodes (OLEDs). Recent research from Japan sheds new light on why: impurities present in the vacuum chamber during fabrication but in amounts so small that they are easily overlooked. Organic light-emitting diodes use a stack of organic layers to convert electricity into light, and these organic layers are most commonly fabricated by heating source materials in vacuum to evaporate and deposit them onto a lower temperature substrate. While issues affecting the efficiency of OLEDs are already well understood, a complete picture of exactly how and why OLEDs degrade and lose brightness over time is still missing. Complicating matters is that devices fabricated with seemingly the same procedures and conditions but by different research groups often degrade at vastly different rates even when the initial performance is the same. Unable to attribute these reproducibility issues to known sources such as the amount of residual water in the chamber and the purity of the starting materials, a report published online in Scientific Reports on December 13, 2016, adds a new piece to the puzzle by focusing on the analysis of the environment in the vacuum chamber. "Although we often idealize vacuums as being clean environments, we detected many impurities floating in the vacuum even when the deposition chamber is at room temperature," says lead author Hiroshi Fujimoto, chief researcher at Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA) and visiting associate professor of Kyushu University. Because of these impurities in the deposition chamber, the researchers found that the time until an OLED under operation dims by a given amount because of degradation, known as the lifetime, sharply increased for OLEDs that spent a shorter time in the deposition chamber during fabrication. This trend remained even after considering changes in residual water and source material purity, indicating the importance of controlling and minimizing the device fabrication time, a rarely discussed parameter. Research partners at Sumika Chemical Analysis Service Ltd. (SCAS) confirmed an increase of accumulated impurities with time by analyzing the materials that deposited on extremely clean silicon wafers that were stored in the deposition chamber when OLED materials were not being evaporated. Using a technique called liquid chromatography-mass spectrometry, the researchers found that many of the impurities could be traced to previously deposited materials and plasticizers from the vacuum chamber components. "Really small amounts of these impurities get incorporated into the fabricated devices and are causing large changes in the lifetime," says Professor Chihaya Adachi, director of Kyushu University's Center for Organic Photonics and Electronics Research (OPERA), which also took part in the study. In fact, the new results suggest that the impurities amount to less than even a single molecular layer. To improve lifetime reproducibility, a practice often adopted in industry is the use of dedicated deposition chambers for specific materials, but this can be difficult in academic labs, where often only a limited number of deposition systems are available for testing a wide variety of new materials. In these cases, deposition chamber design and cleaning in addition to control of the deposition time are especially important. "This is an excellent reminder of just how careful we need to be to do good, reproducible science," comments Professor Adachi. For more information, see "Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes," Scientific Reports 6, 38482 (2016); doi: 10.1038/srep38482. This work was performed by research groups at Kyushu University's Center for Organic Photonics and Electronics Research (OPERA), the Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), and the Institute of System, Information Technology and Nanotechnology (ISIT) in cooperation with Sumika Chemical Analysis Service Ltd. (SCAS). This research is ongoing in part under the Adachi Molecular Exciton Engineering Project funded by the Exploratory Research for Advanced Technology (ERATO) program of the Japan Science and Technology Agency (JST).


Matsui H.,Japan National Institute of Advanced Industrial Science and Technology | Kumaki D.,Yamagata University | Takahashi E.,Sumika Chemical Analysis Service Ltd. | Takimiya K.,Hiroshima University | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Microscopic charge dynamics inside microcrystal domains and across domain boundaries in polycrystalline organic thin-film transistors (OTFTs) were resolved by angle- and temperature-dependent field-induced electron spin resonance (FI-ESR) spectroscopy. We utilized small-molecule and polymer-based polycrystalline OTFTs, both of which are composed of planar microdomains oriented uniaxially on the substrates. Two types of motional narrowing effect are observed at magnetic fields perpendicular and parallel to the substrate: In the former, we observed the motional narrowing effect due to intradomain transport, while in the latter, we observed another motional narrowing effect due to the carrier hopping across the domain boundaries, which averaged out the variation in g factors between respective microdomains. The analyses revealed that the activation energies for the intradomain transport are between 5 and 21 meV, while those for the interdomain carrier hopping are between 45 and 90 meV. The latter ones coincide with those for the apparent mobility for the respective OTFTs. These results demonstrate that the charge transport is limited by the domain boundaries, which form rate-determining barrier potential both in small-molecule and polymer-based polycrystalline OTFTs. © 2012 American Physical Society.


Sailstad J.M.,NC Associates | Amaravadi L.,Biogen Idec | Clements-Egan A.,Janssen Research and Development Johnson and Johnson | Gorovits B.,Pfizer | And 8 more authors.
AAPS Journal | Year: 2014

The Global Bioanalysis Consortium (GBC) set up an international team to explore the impact of immunogenicity on pharmacokinetic (PK) assessments. The intent of this paper is to define the field and propose best practices when developing PK assays for biotherapeutics. We focus on the impact of anti-drug antibodies (ADA) on the performance of PK assay leading to the impact on the reported drug concentration and exposure. The manuscript describes strategies to assess whether the observed change in the drug concentration is due to the ADA impact on drug clearance rates or is a consequence of ADA interference in the bioanalytical method applied to measure drug concentration. This paper provides the bioanalytical scientist guidance for developing ADA-tolerant PK methods. It is essential that the data generated in the PK, ADA, pharmacodynamic and efficacy/toxicity evaluations are viewed together. Therefore, the extent for the investigation of the PK sensitivity to the presence of ADA should be driven by the project needs and risk based. © 2014 American Association of Pharmaceutical Scientists.


Yasuhara M.,University of Hong Kong | Yasuhara M.,Smithsonian Institution | Yasuhara M.,Kochi University | Hunt G.,Smithsonian Institution | And 5 more authors.
Paleobiology | Year: 2012

There is growing evidence that changes in deep-sea benthic ecosystems are modulated by climate changes, but most evidence to date comes from the North Atlantic Ocean. Here we analyze new ostracod and published foraminiferal records for the last 250,000 years on Shatsky Rise in the North Pacific Ocean. Using linear models, we evaluate statistically the ability of environmental drivers (temperature, productivity, and seasonality of productivity) to predict changes in faunal diversity, abundance, and composition. These microfossil data show glacial-interglacial shifts in overall abundances and species diversities that are low during glacial intervals and high during interglacials. These patterns replicate those previously documented in the North Atlantic Ocean, suggesting that the climatic forcing of the deep-sea ecosystem is widespread, and possibly global in nature. However, these results also reveal differences with prior studies that probably reflect the isolated nature of Shatsky Rise as a remote oceanic plateau. Ostracod assemblages on Shatsky Rise are highly endemic but of low diversity, consistent with the limited dispersal potential of these animals. Benthic foraminifera, by contrast, have much greater dispersal ability and their assemblages at Shatsky Rise show diversities typical for deep-sea faunas in other regions. Statistical analyses also reveal ostracod-foraminferal differences in relationships between environmental drivers and biotic change. Rarefied diversity is best explained as a hump-shaped function of surface productivity in ostracods, but as having a weak and positive relationship with temperature in foraminifera. Abundance shows a positive relationship with both productivity and seasonality of productivity in foraminifera, and a hump-shaped relationship with productivity in ostracods. Finally, species composition in ostracods is influenced by both temperature and productivity, but only a temperature effect is evident in foraminifera. Though complex in detail, the global-scale link between deep-sea ecosystems and Quaternary climate changes underscores the importance of the interaction between the physical and biological components of paleoceanographical research for better understanding the history of the biosphere. © 2012 The Paleontological Society.


News Article | December 28, 2016
Site: phys.org

Organic light-emitting diodes use a stack of organic layers to convert electricity into light, and these organic layers are most commonly fabricated by heating source materials in vacuum to evaporate and deposit them onto a lower temperature substrate. While issues affecting the efficiency of OLEDs are already well understood, a complete picture of exactly how and why OLEDs degrade and lose brightness over time is still missing. Complicating matters is that devices fabricated with seemingly the same procedures and conditions but by different research groups often degrade at vastly different rates even when the initial performance is the same. Unable to attribute these reproducibility issues to known sources such as the amount of residual water in the chamber and the purity of the starting materials, a report published online in Scientific Reports on December 13, 2016, adds a new piece to the puzzle by focusing on the analysis of the environment in the vacuum chamber. "Although we often idealize vacuums as being clean environments, we detected many impurities floating in the vacuum even when the deposition chamber is at room temperature," says lead author Hiroshi Fujimoto, chief researcher at Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA) and visiting associate professor of Kyushu University. Because of these impurities in the deposition chamber, the researchers found that the time until an OLED under operation dims by a given amount because of degradation, known as the lifetime, sharply increased for OLEDs that spent a shorter time in the deposition chamber during fabrication. This trend remained even after considering changes in residual water and source material purity, indicating the importance of controlling and minimizing the device fabrication time, a rarely discussed parameter. Research partners at Sumika Chemical Analysis Service Ltd. (SCAS) confirmed an increase of accumulated impurities with time by analyzing the materials that deposited on extremely clean silicon wafers that were stored in the deposition chamber when OLED materials were not being evaporated. Using a technique called liquid chromatography-mass spectrometry, the researchers found that many of the impurities could be traced to previously deposited materials and plasticizers from the vacuum chamber components. "Really small amounts of these impurities get incorporated into the fabricated devices and are causing large changes in the lifetime," says Professor Chihaya Adachi, director of Kyushu University's Center for Organic Photonics and Electronics Research (OPERA), which also took part in the study. In fact, the new results suggest that the impurities amount to less than even a single molecular layer. To improve lifetime reproducibility, a practice often adopted in industry is the use of dedicated deposition chambers for specific materials, but this can be difficult in academic labs, where often only a limited number of deposition systems are available for testing a wide variety of new materials. In these cases, deposition chamber design and cleaning in addition to control of the deposition time are especially important. "This is an excellent reminder of just how careful we need to be to do good, reproducible science," comments Professor Adachi. Explore further: Lifetime breakthrough promising for low-cost and efficient OLED displays and lights More information: Hiroshi Fujimoto et al, Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes, Scientific Reports (2016). DOI: 10.1038/srep38482


Zhou Y.,Kanazawa University | Taima T.,Kanazawa University | Taima T.,Japan Science and Technology Agency | Miyadera T.,Japan Science and Technology Agency | And 5 more authors.
Applied Physics Letters | Year: 2012

We demonstrate phase separation of co-evaporated zinc phthalocyanine (ZnPc) and fullerene (C 60) for efficient organic photovoltaic cells. With introducing a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film and a crystalline copper iodide film on indium tin oxide, 20-nm-thick ZnPc film adopts a lying-down crystalline geometry with grain sizes of about 50 nm. This surface distributed with strong interaction areas and weak interaction areas enables the selective growth of ZnPc and C 60 molecules during following co-evaporation, which not only results in a phase separation but also improve the crystalline growth of C 60. This blend film greatly enhances the efficiencies in photocurrent generation and carrier transport, resulting in a high power conversion efficiency of 4.56 under 1 sun. © 2012 American Institute of Physics.


Zhou Y.,Kanazawa University | Taima T.,Kanazawa University | Taima T.,Japan Science and Technology Agency | Miyadera T.,Japan Science and Technology Agency | And 5 more authors.
Nano Letters | Year: 2012

We report a simple method to achieve efficient nanostructured organic photovoltaics via patterning copper iodide (CuI) nanocrystals on indium tin oxide by glancing angle deposition. The strong interfacial interaction between zinc phthalocyanine (ZnPc) and CuI leads to the formation of nanopillar arrays with lying-down molecular order, which greatly improve light absorption and surface roughness for exciton dissociation. Optimized ZnPc/C 60 bilayer cell has a power conversion efficiency of 4.0 ± 0.1%, which is about 3-fold larger than that of conventional planar cell. © 2012 American Chemical Society.


Asako H.,Sumitomo Chemical | Shimizu M.,Sumika Chemical Analysis Service Ltd | Makino Y.,Toyama Prefectural University | Itoh N.,Toyama Prefectural University
Tetrahedron Letters | Year: 2010

An effective method for producing methyl 4-bromo-3-hydroxybutyrate enantiomers was developed using an engineered protein. Escherichia coli transformant cells containing a mutant β-keto ester reductase (KER-L54Q) from Penicillium citrinum and a cofactor-regeneration enzyme such as glucose dehydrogenase (GDH) or Leifsonia sp. alcohol dehydrogenase (LSADH) were used to produce methyl (S)-4-bromo-3-hydroxybutyrate from methyl 4-bromo-3-oxobutyrate. On the other hand, the production of methyl (R)-4-bromo-3-hydroxybutyrate was achieved by asymmetric reduction of methyl 4-bromo-3-oxobutyrate with a mutant phenylacetaldehyde reductase (PAR-HAR1) from Rhodococcus sp. ST-10. © 2010 Elsevier Ltd. All rights reserved.


Tokunaga T.,Sumitomo Chemical | Okamoto M.,Sumitomo Chemical | Tanaka K.,Sumitomo Chemical | Tanaka K.,Sumika Chemical Analysis Service Ltd. | And 2 more authors.
Analytical Chemistry | Year: 2010

Chiral separation by high performance liquid chromatography (Chiral HPLC) is one of the most powerful methods for estimating optical and chemical purity of chiral compounds. However, it has a weakness in that much time and effort are required to prepare authentic samples. A novel chiral liquid chromatography-circular dichroism-NMR (LC-CD-NMR) technique, on the other hand, requires only crude chiral compounds that include enantiomers as minor impurities. In this study, chiral LC-CD-NMR was constructed by connecting a conventional LC-NMR system with a CD detector. A pyridylalanine derivative mixture was prepared to mimic technical grade material in an early phase of development. By chiral LC-CD-NMR, the enantiomer peak is identified by an opposite sign of the CD Cotton effect curve and an identical 1H NMR spectrum to that of the main component. Using NMR as a detector, this method is superior in ability to discriminate enantiomers from other isomers indistinguishable by MS. Furthermore, this method is also applicable for selecting the best separation conditions of chiral HPLC. The degrees of separation (Rs) between the main component and its enantiomer in several chiral columns were compared. Even with modern chromatographic methods, establishing the best chiral HPLC conditions in an early phase of development is difficult: chiral LC-CD-NMR is a suitable solution. © 2010 American Chemical Society.


Shiraishi K.,Sumika Chemical Analysis Service Ltd | Matsuzaki K.,Sumika Chemical Analysis Service Ltd | Matsumoto A.,Sumika Chemical Analysis Service Ltd | Hashimoto Y.,Sumika Chemical Analysis Service Ltd | Iba K.,Sumika Chemical Analysis Service Ltd
Journal of Oleo Science | Year: 2010

Desmosine (DES) and isodesmosine (IDES) are both pyridinium amino acid isomers that serve as cross-linking molecules binding the polymeric chains of amino acids into elastin. Found in urine, they are markers for the degradation of elastin which occurs in chronic obstructive pulmonary disease (COPD). In this study, a robust method using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) with selected reaction monitoring (SRM) mode was developed for the analysis of DES and IDES in human urine. Pyridylethyl-cysteine (PE-Cys) as internal standard (I.S.) was employed for the quantification of DES and IDES. The analytes and I.S. were extracted by solid-phase extraction with Oasis MCX cartridges and separated on an AccQ-Tag Ultra column. The assay was accurate (-6.8% to 14.5%) and precise (2.8% to 13.8%) within the concentration range of 1 to 250 pmol/mL. Moreover, the recovery and stability (working/ I.S. solution, urine samples with added elastin, and pretreated sample) was investigated, and these parameters were found acceptable. The UPLC-MS/MS method was validated and had good reproducibility and stability for the quantification of DES and IDES, which requires only 100 mL of human urine. This assay will be a useful means for measuring DES and IDES levels in urine with robustness and characterizing patients with COPD. © 2010 by Japan Oil Chemists' Society.

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