bluuebunny/crossref_metadata_2025_split huggingface dataset:
Designing a Stable Cathode with Multiple Layers to Improve the Operational Lifetime of Polymer Light‐Emitting Diodes
Authors: Lee Tae‐Woo , Kim Mu‐Gyeom , Park Sang Hun , Kim Sang Yeol , Kwon Ohyun , Noh Taeyong , Park Jong‐Jin , Choi Tae‐Lim , Park Jong Hyeok , Chin Byung Doo 
Published: May 2009

AbstractThe short device lifetime of blue polymer light‐emitting diodes (PLEDs) is still a bottleneck for commercialization of self‐emissive full‐color displays. Since the cathode in the device has a dominant influence on the device lifetime, a systematic design of the cathode structure is necessary. The operational lifetime of blue PLEDs can be greatly improved by introducing a three‐layer (BaF2/Ca/Al) cathode compared with conventional two‐layer cathodes (BaF2/Al and Ba/Al). Therefore, the roles of the BaF2 and Ca layers in terms of electron injection, luminous efficiency, and device lifetime are here investigated. For efficient electron injection, the BaF2 layer should be deposited to the thickness of at least one monolayer (∼3 nm). However, it is found that the device lifetime does not show a strong relation with the electron injection or luminous efficiency. In order to prolong the device lifetime, sufficient reaction between BaF2 and the overlying Ca layer should take place during the deposition where the thickness of each layer is around that of a monolayer.
One‐Dimensional Microwires Formed by the Co‐Assembly of Complementary Aromatic Donors and Acceptors
Authors: Wang Jie‐Yu , Yan Jing , Ding Lin , Ma Yuguo , Pei Jian 
Published: May 2009

AbstractA truxene derivative (Tr3) with a C3 symmetric conjugated plane is synthesized; this derivative is a perfect match, in both size and structure, with its oxidized counterpart, the truxenone derivative (TrO3), a new electron acceptor that was recently reported. The complementary pair, Tr3 and TrO3, sets a good platform for the investigation of aromatic donor–acceptor interactions. Detailed 1H NMR experiments, photoluminescence spectroscopy, as well as differential scanning calorimetry are performed to investigate the interaction between Tr3 and TrO3, from solution to mesophase. One‐dimensional microbelts readily formed from a 1:1 mixture of Tr3 and TrO3. Scanning electron microscopy, powder X‐ray diffraction, as well as fluorescence microscopy are performed to elucidate their co‐assembly structure in the solid state. Moreover, modulation of the co‐assembly structure is easily realized by changing the concentration or mixing ratio. The present system opens the possibility of forming 1D heterostructures via electron donor–acceptor interaction, and its potential application as P–N junction and photowaveguide materials in optoelectronic devices.
Doping of Conjugated Polythiophenes with Alkyl Silanes
Authors: Kao Chi Yueh , Lee Bumsu , Wielunski Leszek S. , Heeney Martin , McCulloch Iain , Garfunkel Eric , Feldman Leonard C. , Podzorov Vitaly 
Published: May 2009

AbstractA strong modification of the electronic properties of solution‐processable conjugated polythiophenes by self‐assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1 ± 0.1) × 103 S cm−1 for poly(2,5‐bis(3‐tetradecylthiophen ‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and 50 ± 20 S cm−1 for poly(3‐hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self‐polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM‐induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM‐doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors.
Knowledge‐Based Approach towards Hydrolytic Degradation of Polymer‐Based Biomaterials
Authors: Hofmann Dieter , Entrialgo‐Castaño Maria , Kratz Karl , Lendlein Andreas 
Published: May 2009

AbstractThe concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.1 A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge‐based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir–Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided.
Exploiting the Kubas Interaction in the Design of Hydrogen Storage Materials
Authors: Hoang Tuan K. A. , Antonelli David M. 
Published: May 2009

AbstractHydrogen adsorption and storage using solid‐state materials is an area of much current research interest, and one of the major stumbling blocks in realizing the hydrogen economy. However, no material yet researched comes close to reaching the DOE 2015 targets of 9 wt% and 80 kg m−3 at this time. To increase the physisorption capacities of these materials, the heats of adsorption must be increased to ∼20 kJ mol−1. This can be accomplished by optimizing the material structure, creating more active species on the surface, or improving the interaction of the surface with hydrogen. The main focus of this progress report are recent advances in physisorption materials exhibiting higher heats of adsorption and better hydrogen adsorption at room temperature based on exploiting the Kubas model for hydrogen binding: (η2‐H2)–metal interaction. Both computational approaches and synthetic achievements will be discussed. Materials exploiting the Kubas interaction represent a median on the continuum between metal hydrides and physisorption materials, and are becoming increasingly important as researchers learn more about their applications to hydrogen storage problems.
Physics and Applications of Bismuth Ferrite
Authors: Catalan Gustau , Scott James F. 
Published: May 2009

AbstractBiFeO3 is perhaps the only material that is both magnetic and a strong ferroelectric at room temperature. As a result, it has had an impact on the field of multiferroics that is comparable to that of yttrium barium copper oxide (YBCO) on superconductors, with hundreds of publications devoted to it in the past few years. In this Review, we try to summarize both the basic physics and unresolved aspects of BiFeO3 (which are still being discovered with several new phase transitions reported in the past few months) and device applications, which center on spintronics and memory devices that can be addressed both electrically and magnetically.
Challenges and Progress in High‐Throughput Screening of Polymer Mechanical Properties by Indentation
Authors: Kranenburg Johannes M. , Tweedie Catherine A. , van Vliet Krystyn J. , Schubert Ulrich S. 
Published: May 2009

AbstractDepth‐sensing or instrumented indentation is an experimental characterization approach well‐suited for high‐throughput investigation of mechanical properties of polymeric materials. This is due to both the precision of force and displacement, and to the small material volumes required for quantitative analysis. Recently, considerable progress in the throughput (number of distinct material samples analyzed per unit time) of indentation experiments has been achieved, particularly for studies of elastic properties. Future challenges include improving the agreement between various macroscopic properties (elastic modulus, creep compliance, loss tangent, onset of nonlinear elasticity, energy dissipation, etc.) and their counterpart properties obtained by indentation. Sample preparation constitutes a major factor for both the accuracy of the results and the speed and efficiency of experimental throughput. It is important to appreciate how this processing step may influence the mechanical properties, in particular the onset of nonlinear elastic or plastic deformation, and how the processing may affect the agreement between the indentation results and their macroscopic analogues.
Carbon‐Based Field‐Effect Transistors for Nanoelectronics
Authors: Burghard Marko , Klauk Hagen , Kern Klaus 
Published: May 2009

AbstractIn this review, the suitability of the major types of carbon nanostructures as conducting channels of field‐effect transistors (FETs) is compared on the basis of the dimensionality and size of their π‐conjugated system. For each of these materials, recent progress in its synthesis, electrical and structural characterization, as well as its implementation into various gate configurations is surveyed, with emphasis laid onto nanoscale aspects of the FET design and the attainable device performance. Finally, promising future research directions, such as the integration of different carbon nanostructures into novel device architectures, are outlined.
Kohärente mehrdimensionale Schwingungsspektroskopie von Biomolekülen: Konzepte, Simulationen und Herausforderungen
Authors: Zhuang Wei , Hayashi Tomoyuki , Mukamel Shaul 
Published: May 2009

AbstractDie Schwingungsantwort komplexer Moleküle auf Sequenzen von Infrarotpulsen liefert Momentaufnahmen ihrer Struktur und Dynamik im Femtosekundenbereich. Diese Technik, die analog ist zur mehrdimensionalen NMR‐Spektroskopie und Korrelationen von Bewegungsvorgängen während kontrollierter Zeitintervalle abbildet (siehe Schema), wurde zur Untersuchung von Proteinfaltungen, Wasserstoffbrücken, Lipidmembranen und chemischen Umlagerungen genutzt.magnified imageDie Schwingungsanregung komplexer Biomoleküle mit Femtosekunden‐Infrarotpulsen ermöglicht einzigartige Einblicke in ihre Struktur, Dynamik und fluktuierende Umgebung. Dieser Aufsatz stellt die Grundlagen moderner zweidimensionaler Infrarot(2DIR)‐Methoden vor, die analog sind zu den Techniken der mehrdimensionalen NMR‐Spektroskopie. Störungstheoretische Ansätze zur Berechnung der nichtlinearen optischen Eigenschaften von gekoppelten lokalisierten Chromophoren werden eingeführt und auf Schwingungsübergänge im Amidrückgrat von Proteinen, flüssigem Wasser, Membranlipiden und Amyloidfibrillen angewendet. Die Signalanalyse erfolgt durch klassische Moleküldynamiksimulationen in Kombination mit einem fluktuierenden Hamilton‐Operator für gekoppelte lokalisierte anharmonische Schwingungen, dessen Abhängigkeit von der lokalen elektrostatischen Umgebung durch Ab‐initio‐Daten parametrisiert wird. Die verwendeten Simulationsverfahren (Kumulanten‐Entwicklung von Gauß‐Fluktuationen, Streuung von Quasipartikeln, stochastische Liouville‐Gleichungen, direkte numerische Reihenentwicklungen) sind in den SPECTRON‐Code integriert, der eine Schnittstelle mit Standardmoleküldynamikmethoden hat. Ebenfalls diskutiert werden chiralitätsinduzierte Techniken zur Auflösungssteigerung sowie die Signaturen von konformativen und H‐Brücken‐Fluktuationen, Proteinfaltungsvorgängen und chemischen Austauschprozessen.
Protein Conformational Flexibility from Structure‐Free Analysis of NMR Dipolar Couplings: Quantitative and Absolute Determination of Backbone Motion in Ubiquitin
Authors: Salmon Loïc , Bouvignies Guillaume , Markwick Phineus , Lakomek Nils , Showalter Scott , Li Da‐Wei , Walter Korvin , Griesinger Christian , Brüschweiler Rafael , Blackledge Martin 
Published: May 2009

AbstractEin zuverlässiges Verfahrenzur Bestimmung der Bewegungen des Proteingerüsts über einen Zeitraum von Piko‐ bis Millisekunden auf der Grundlage dipolarer Restkopplungen erfordert keine Skalierung mithilfe einer externen Referenz. Die Ergebnisse für Ubiquitin (blau im Graph: experimentelle N‐HN‐Ordnungsparameter) entsprechen in Amplitude, Art und Verteilung sehr gut der Bewegung, die in einer 400‐ns‐Moleküldynamiktrajektorie von Ubiquitin ermittelt wurde (rot).magnified image
Komplexe mit dativen Bindungen zwischen d‐ und s‐Block‐Metallen: Synthese und Struktur von [(Cy3P)2Pt‐Be(Cl)X] (X=Cl, Me)
Authors: Braunschweig Holger , Gruss Katrin , Radacki Krzysztof 
Published: May 2009

AbstractEin Platin‐Beryllium‐Addukt (siehe Bild) wurde durch Reaktion von [Pt(PCy3)2] mit BeCl2 erhalten. Die Umsetzung mit Methyllithium führte zur Substitution eines Liganden am Berylliumzentrum. Beide Komplexe wurden strukturell charakterisiert und zeichnen sich durch eine präzedenzlose Zwei‐Zentren‐zwei‐Elektronen‐Bindung zwischen einem Übergangsmetall und Beryllium aus.magnified image
Stereocontrolled Synthesis of Highly Functionalized Quaternary Carbon Centers: A Route to α‐Substituted Serines
Authors: Ariza Xavier , Cornellà Josep , Font‐Bardia Mercè , Garcia Jordi , Ortiz Jordi , Sánchez Carolina , Solans Xavier 
Published: May 2009

AbstractDrei in einer Reihe! Hoch funktionalisierte quartäre Aminopolyole mit drei benachbarten asymmetrischen Kohlenstoffzentren wurden durch Tandem‐Hydroborierung des Allens 1 und Addition an ein Aldehyd hergestellt (siehe Schema; Cy=Cyclohexyl, TBDPS=tert‐Butyldiphenylsilyl, Ts=4‐Toluolsulfonyl). Dieser Eintopfprozess bietet Zugang zu fortgeschrittenen Zwischenprodukten für die enantioselektive Synthese von α‐substituierten Serinen.magnified image
Sequenzierung einzelner DNA‐Moleküle in Echtzeit
Authors: Ibach Jenny , Brakmann Susanne 
Published: May 2009

AbstractKleiner geht's nicht: Durch direkte Beobachtung einer DNA‐Polymerase‐basierten “Sequenziermaschine” mithilfe von Einzelmolekültechniken gelang kürzlich eine Sequenzierung durch Synthese in Echtzeit. Nucleotide mit einer Fluoreszenzmarkierung am 5′‐Phosphatrest und Nullmode‐Lichtwellenleiter waren entscheidend für den Erfolg dieses Experiments, das ein kostengünstiges Verfahren zur Genomsequenzanalyse verspricht.magnified image
N‐Heterocyclic Carbenes as Efficient Organocatalysts for CO2 Fixation Reactions
Authors: Kayaki Yoshihito , Yamamoto Masafumi , Ikariya Takao 
Published: May 2009

AbstractFixe Idee: N‐Heterocyclische Carbene und ihre CO2‐Addukte sind wirksame Organokatalysatoren für die Synthese von Carbonaten durch Addition von CO2 an Propargylalkohole oder Epoxide unter milden, lösungsmittelfreien Bedingungen (siehe Schema). Die erhöhte Lewis‐Basizität von Imidazol‐2‐ylidenen mit elektronenschiebenden N,N′‐Dialkylgruppen macht es möglich, CO2 als nucleophiles Fragment in chemischen Fixierungsprozessen einzusetzen.magnified image
A Supramolecularly Assisted Transformation of Block‐Copolymer Micelles into Nanotubes
Authors: Kim Sung Ho , Nederberg Fredrik , Jakobs Robert , Tan Jeremy P. K. , Fukushima Kazuki , Nelson Alshakim , Meijer E. W. , Yang Yi Yan , Hedrick James L. 
Published: May 2009

AbstractOnce around the block: Incorporation of a rigid hydrogen‐bonding benzamide unit, placed at the interface between two polymer blocks, in poly(ethylene glycol) (PEG)–(thio)urea–poly(L‐lactide) (PLLA) block copolymers transforms the morphology of the block copolymers, from spherical micelles, as formed by PEG‐PLLA diblock copolymers, into nanotubes in solution.magnified image
Enantioselective Synthesis of β‐Iodo Morita–Baylis–Hillman Esters by a Catalytic Asymmetric Three‐Component Coupling Reaction
Authors: Senapati Bidyut Kumar , Hwang Geum‐Sook , Lee Sungil , Ryu Do Hyun 
Published: May 2009

AbstractA catalytic route toward chiral Morita–Baylis–Hillman esters by asymmetric coupling between α,β‐acetylenic esters, aldehydes, and trimethylsilyl iodide has been developed (see scheme). The reaction proceeds with high to excellent enantioselectivities, and the products can be transformed into β‐branched derivatives in a single step and with excellent retention of configuration. TMS=trimethylsilylmagnified image
Protein Conformational Flexibility from Structure‐Free Analysis of NMR Dipolar Couplings: Quantitative and Absolute Determination of Backbone Motion in Ubiquitin
Authors: Salmon Loïc , Bouvignies Guillaume , Markwick Phineus , Lakomek Nils , Showalter Scott , Li Da‐Wei , Walter Korvin , Griesinger Christian , Brüschweiler Rafael , Blackledge Martin 
Published: May 2009

AbstractA robust procedurefor the determination of protein‐backbone motions on time scales of pico‐ to milliseconds directly from residual dipolar couplings has been developed that requires no additional scaling relative to external references. The results for ubiquitin (blue in graph: experimental NHN order parameters) correspond closely to the amplitude, nature, and distribution of motion found in a 400 ns molecular‐dynamics trajectory of ubiquitin (red).magnified image
Complexes with Dative Bonds between d‐ and s‐Block Metals: Synthesis and Structure of [(Cy3P)2PtBe(Cl)X] (X=Cl, Me)
Authors: Braunschweig Holger , Gruss Katrin , Radacki Krzysztof 
Published: May 2009

AbstractA platinum–beryllium adduct (see structure) was prepared by the reaction of [Pt(PCy3)2] and BeCl2. Treatment with methyllithium resulted in ligand substitution at the beryllium center. Both complexes were structurally characterized and display unprecedented two‐center two‐electron bonds between a transition metal and beryllium.magnified image
N‐Heterocyclic Carbenes as Efficient Organocatalysts for CO2 Fixation Reactions
Authors: Kayaki Yoshihito , Yamamoto Masafumi , Ikariya Takao 
Published: May 2009

AbstractGetting a fix: N‐heterocyclic carbenes (NHCs) and NHC–CO2 adducts serve as potent organocatalysts for carbonate synthesis by the addition of a CO2 unit to propargylic alcohols or epoxides under mild and solvent‐free reaction conditions (see scheme). The enhanced Lewis basicity of imidazol‐2‐ylidenes bearing electron‐donating alkyl groups on the nitrogen atoms leads to utilizing CO2 as a nucleophilic fragment in the chemical fixation processes.magnified image
Cover Picture: Substituent‐Free Gallium by Hydrogenolysis of Coordinated GaCp*: Synthesis and Structure of Highly Fluxional [Ru2(Ga)(GaCp*)7(H)3] (Angew. Chem. Int. Ed. 21/2009)
Authors: Cadenbach Thomas , Gemel Christian , Schmid Rochus , Halbherr Markus , Yusenko Kirill , Cokoja Mirza , Fischer Roland A. 
Published: May 2009

AbstractSoft skin, hard core …︁ is the basic principle for the formation of a nano‐alloy from molecular precursors. The co‐hydrogenolysis of ruthenium complexes in presence of GaCp* gives the isolable key intermediate [Ru2(Ga)(GaCp*)7(H)3] featuring a substituent‐free bridging gallium atom. From this “embryonic” species Ru/Ga phases are formed by complete cleavage of the protective Cp* shell (depicted as an eggshell in the Cover picture), as described by R. A. Fischer et al. in their Communication on page 3872 ff.magnified image
Inside Cover: Giant Pores in a Chromium 2,6‐Naphthalenedicarboxylate Open‐Framework Structure with MIL‐101 Topology (Angew. Chem. Int. Ed. 21/2009)
Authors: Sonnauer Andreas , Hoffmann Frank , Fröba Michael , Kienle Lorenz , Duppel Viola , Thommes Matthias , Serre Christian , Férey Gérard , Stock Norbert 
Published: May 2009

AbstractHighly porous and stable metal–organic frameworks, isoreticular to MIL‐101 and with cage diameters of 39 and 46 Å, are obtained by replacement of the 1,4‐benzenedicarboxylate ligands in that framework with 2,6‐naphthalenedicarboxylate. In their Communication on page 3791 ff., N. Stock and co‐workers report high‐throughput methods used to optimize reaction conditions and characterization of this MTN zeolite analogue by a combination of structure simulation, electron microscopy, and sorption measurements.magnified image
Structural development Of TMMA and SSQXN‐8 as porous chelating resins
Authors: Ibrahim Gehan M. , Ahmad Mohamed I. , El‐Gammal Belal 
Published: May 2009

AbstractSuperfast kinetics of Nd+3, Eu+3, and Gd+3 ions were studied on the surfaces of N,N,N\,N\‐tetramethylmalonamide (TMMA) and silsesquioxane (SSQXN‐8) resins. TMMA and SSQXN‐8 were prepared by suspension polymerization and sol–gel routes, respectively. They were identified using elemental analysis, FTIR, H‐NMR, 13C‐NMR, MIP, and BET surface area. Kinetic investigations were performed in batch conditions and different models were used to fit the data; Boyd and Helfferich models were found the best. The diffusion of the ions through the resins were very fast and found to be in the order of 10−16 m2/S. Effective diffusions of the studied ions were found to be 10−15 order of magnitude and directly proportional to the kinetic energy of the transition state. ΔS* values from −166.044 to −179.297 J mol−1 K−1 were estimated as entropy stability factors of the system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation of a polyimide composite filled with corundum as a kind of precision grinding slice
Authors: Qingsudu Si , Chen Chen , Xianghua Xie , Yaming Dong 
Published: May 2009

AbstractBy using a two‐step synthetic method, a novel grinding material, SiC and polyimide grinding slice, is prepared. This grinding slice can be used for mechanical planarization of hard and brittle materials, such as silicon, optical glass, advanced ceramics, specials metal, jewelry, disks etc. For observing the physical and chemical properties of the slice, scanning electron microscopy, FTIR spectroscopy, thermal gravimetric analysis, tensile strength, and elongation at break are used. All the experimental data indicate that the SiC/PI slice will be a very useful grinding material for obtaining a precision surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Molecular imprinted solid‐phase extraction of huperzine A from Huperzia Serrata
Authors: Wang Guosong , Cao Qiue , Zhu Xiufang , Yang Xueqiong , Yang Minghui , Ding Zhongtao 
Published: May 2009

AbstractOn the basis of the non‐covalent interaction between template and monomer, porous molecularly imprinted polymers (MIPs) were synthesized by a thermal‐initiated polymerization method using huperzine A as template, acrylamide, or methacrylic acid as function monomer, ethylene glycol dimethacrylate as cross‐linking agent. The interaction between template and functional monomers was studied by UV spectrophotometry, which showed a formation of huperzine A‐monomer complexes with stoichiometric ratio of 1 : 2 in the pre‐polymerized systems. The resultant MIP particles were tested in the equilibrium binding experiment to analyze their adsorption ability to huperzine A, and were characterized by Fourier Transform Infrared (FTIR) study. The recognition properties of MIP were estimated in solid‐phase extraction by selecting four compounds (isolated from the Chinese herb Huperzia serrata) as substrates, and were compared with and prior to those of the NIP. High affinity and adsorption of MIP1 which was prepared in chloroform with huperzine A as imprinted molecule, and acrylamide (AM) as functional monomer, made an attractive application of MIP1 in separation processes. In final, using MIP1 solid‐phase extraction micro‐column, huperzine A was enriched and separated from the real extraction sample of Huperzia serrata. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009