bluuebunny/crossref_metadata_2025_split huggingface dataset:
White Electroluminescent Devices Using Polymer Blends
Authors: Hwang Do-Hoon , Lee Jeong-Ik , Lee Chang-Hee 
Published: June 2019

AbstractWhite light-emitting devices were fabricated using the blends of blue, green, red emissive polymers of poly[9,9-(2'-ethylhexyl)fluorene] (PEHF), poly(9,9-dioctylfluorene-2,7-vinylene) (POFV), poly(2-(3',7'-dimethyloctyloxy)-5-methoxy-1,4-phenylene-1-cyanovinylene) (CNPPV) and poly(2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV). Inefficient energy transfers between the blue polymer and the green or the red polymer, which was observed in PL spectra of the blend films, provides a good opportunity to get white light emission due to better blend ratio controllability. The EL devices were fabricated with ITO/PEDOT/blend/Ca/Al configuration and good white light-emission was obtained for a certain blend ratio. The light-emission was observable from 4V and a maximum brightness of 400 cd/m2 was obtained with the device.
Double-Excitation Dynamics in m-LPPP probed with sub-20 fs Time Resolution
Authors: Gadermaier C. , Cerullo G. , Manzoni C. , Scherf U. , List E.J.W. , Lanzani G. 
Published: June 2019

AbstractIn a novel modification of transient differential transmission spectroscopy, the first excited state S1 is reexcited via a second laser pulse towards a higher lying state Sn. The dynamics of the relaxation of this state Sn as well as the states created from Sn are revealed by a broad-band probe pulse.We find that the charge carrier generation efficiency from Sn is higher compared to S1. The push and probe durations below 20 fs enable the temporal resolution of the ultrafast relaxation of the Sn state and enables us to identify the two main contributions to enhanced charge generation from Sn, energy migration towards sites of high dissociation probability, and exciton dissociation during vibrational relaxation.
High pressure studies on the packing forces and intermolecular interaction in polyphenyls
Authors: Heimel G. , Puschnig P. , Oehzelt M. , Hummer K. , Koppelhuber-Bitschnau B. , Porsch F. , Ambrosch-Draxl C. , Resel R. 
Published: June 2019

AbstractIn this work, we report on pressure induced structural changes in crystalline oligo(paraphenylenes) containing two to six phenyl rings. Revisiting the crystal structures at ambient conditions reveals details in the packing principle. A linear relationship between the density at ambient conditions and the number of phenyl rings is found. Energy dispersive X-ray diffraction has been performed in a systematic study on polycrystalline powders of biphenyl, paraterphenyl, p-quaterphenyl, p-quinquephenyl and p-sexiphenyl under hydrostatic pressure up to 60 kbar. Our investigations not only yield pressure dependent lattice parameters and hints towards pressure induced changes in the molecular arrangement, but also allow for an analysis of the equations of state of these substances as a function of oligomer length. We report the previously unknown bulk modulus of p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl (B0 = 83 kbar, 93 kbar, and 100 kbar respectively) and its pressure derivative (B0' = 6.4, 7.5, and 5.6). A linear dependence of the bulk modulus on the inverse number of phenyl rings in the molecules is found.
Spectroscopic Photovoltage Chracterization of PPV Thin Films Suitable for Pled Applications
Authors: Samal Girija Sankar , Biswas A.K. , Mohapatra Y. N. 
Published: June 2019

AbstractWe have studied photovoltage spectra of PPV thin films using both conventional single layer LED structure (ITO/PPV/Al), and capacitive structure consisting of ITO/Mica/PPV/ITO films. The photovoltage spectra for both types of devices have sharp features and are identical indicating that the features observed are primarily due to PPV material itself. We observed two sharp peaks in the energy range of 2.5 -2.7 eV (i.e. above HOMO-LUMO gap) in photovoltage spectrum. The lineshape of the peaks strongly suggests that the peaks are most probably associated with photoionization of excitons. Temperature dependence of spectral lineshape of photocurrent peaks has been studied in the range of 80K-300K. The magnitudes of photocurrent peaks are weakly dependent on temperature, while other spectral features such as peak position and peak width are nearly independent of temperature. On the basis of absorbance, photovoltage and PL spectra, we conclude that both polarons and photoionization of excitons contribute to steady state photovoltage spectra.
Characterization of Isomers in Solid Aluminum tris-(Quinoline-8-olate) by 27Al NMR
Authors: Nandagopal Magesh , Mathai Mathew , Papadimitrakopoulos Fotios , Utz Marcel 
Published: June 2019

AbstractAluminum tris-(quinoline-8-olate) (Alq3) is the most widely used electron transport material for organic light emitting diodes. The Alq3 molecule exists as two different isomers: meridianal and facial, which differ by the symmetry of the arrangement of ligands around the aluminum ion. Various crystalline polymorphs of Alq3 have been identified to contain one of these isomers. In this paper we present experimental results that show that the facial and meridianal isomers of Alq3 can be distinguished in the solid state by 27Al nuclear magnetic resonance (NMR) spectroscopy under magic angle spinning (MAS). Our results prove that the recently discovered δ-phase of Alq3 exclusively contains the facial isomer. The same technique is also used to characterize the amorphous deposit of Alq3 showing that it is the meridianal isomer that predominantly exists in the amorphous state.
Charge carrier lifetimes in a smectic liquid crystalline photoconductor of a 2-phenylnaphthalene derivative
Authors: Iino Hiroaki , Hanna Jun-Ichi 
Published: June 2019

AbstractWe have investigated the charge carrier lifetimes for electrons and holes in smectic mesophases of a 2-phenylnaphthalene derivative, 6-(4'-octylphenyl)-2-dodecyloxynaphthalene (8-PNP-O12) by time-of-flight (TOF) measurement. For the negative charge carriers, we found two transits in different time range, which are attributed to electronic and ionic conduction. With the aid of liquid-like fluidity of the material, we could prepare very thick samples over 500μm, and it enables us to determine the carrier lifetimes, which are governed by different regimes: the hole lifetime is governed by recombination of charge carriers and estimated to be 10-2 sec; on the other hand, the electron lifetime is dominated by trapping at deep states and estimated to be on the order of 10-5 sec for both SmA and SmB phases.
A Novel Strategy for the Solid Phase Synthesis of Ultra Pure Organic Semiconductors
Authors: Turner D. , Spivey A. , Cupertino D. , Mackie P. , Anemian R. , Yeates S. 
Published: June 2019

AbstractA new solid phase synthetic strategy for the production of organic semiconductors has been developed. The strategy uses a germanium-based linker and Suzuki-type cross-coupling protocols and has been demonstrated for the iterative synthesis of both a regio-regular oligo-3-alkyl-thiophene and an oligoarylamine. The process also incorporates a novel “doublecoupling” after each iteration which minimizes deletion sequences. The key steps exploits the susceptibility of α-silyl- or α-silyloxy- but not germyl-substituted derivatives toward nucleophilic ipso-protodemetalation.
Oriented Luminescent Nanostructures From Single Molecules Of Conjugated Polymers
Authors: Mehta Adosh , Kumar Pradeep , Zheng Jie , Dickson Robert M. , Sumpter Bobby , Barnes Michael D. 
Published: June 2019

AbstractDipole emission pattern imaging experiments on single chains of common conjugated polymers (solubilized poly phenylene vinylenes) isolated by ink-jet printing techniques have revealed surprising uniformity in transition moment orientation perpendicular to the support substrate. In addition to uniform orientation, these species show a number of striking differences in photochemical stability, polarization anisotropy,[1] and spectral signatures[2] with respect to similar (well-studied) molecules dispersed in dilute thin-films. Combined with molecular mechanics simulation, these results point to a structural picture of a folded macromolecule as a highly ordered cylindrical nanostructure whose long-axis (approximately collinear with the conjugation axis) is oriented, by an electrostatic interaction, perpendicular to the coverglass substrate. These results suggest a number of important applications in nanoscale photonics and molecular-scale optoelectronics.
Electric field pulse assisted covalent immobilization and hybridization of DNA in the nanosecond time scale
Authors: Fixe F. , Branz H.M. , Prazeres D.M.F. , Chu V. , Conde J.P. 
Published: June 2019

AbstractA single, square, voltage pulse is used to accelerate both the immobilization kinetics of DNA molecules on a functionalized thin film silicon dioxide surface and the hybridization of complementary DNA strands to immobilized DNA molecules. The voltage pulse is applied to an integrated thin-film metal electrode beneath the functionalized surface. The duration and magnitude of the voltage pulse are compatible with silicon microelectronics circuits. During immobilization, covalent thiol bonding to the functionalized surface occurs during a single pulse lasting only 100 ns. Hybridization to the immobilized complementary strand occurs during 100 μs pulses.
Mems Tactile Sensors for Surgical Instruments
Authors: Rebello Keith J. , Lebouitz Kyle S. , Migliuolo Michele 
Published: June 2019

AbstractThe development of sophisticated endoscopic tools and the recent introduction of robotics are expanding the applications of minimally invasive surgery. The lack of tactile feedback in the currently available endoscopic and robotic telemanipulation systems however represents a significant limitation. A need has arisen for the development of surgical instruments having integrated sensors. Current efforts to integrate sensors into or onto surgical tools has focused on fabrication of sensors on silicon, polyimide, or some other substrate and then attaching the sensors to a tool by hand or machine with epoxy, tape, or some other glue layer. Attaching the sensor in this manner has certain deficiencies. In particular, this method of attaching sensors to a surgical tool limits the sensors size, increases its thickness, and further constrains where the sensor can be placed. A method of fabricating tactile sensors on surgical instruments that addresses these deficiencies is discussed.
Transimpedance Mode CMOS Microelectrode Array For In-Vitro Neuronal Activity Recording
Authors: Wegman Jacob S. , Dwarka Amar , Holzer Matthew , Lye Whye-Kei , Reed Michael L. , Herzog Erik , Blalock Travis N. 
Published: June 2019

AbstractA CMOS integrated microelectrode array (IMA) utilizing a low-inpedance transimpedance input has been developed. The design uses a three-stage amplifier, including a transimpedance input stage, buffer, and multiplexor. The input stage presents a low impedance which provides bias for the neural input and maximizes the current transfer into the circuit. The amplifiers are replicated in an 8x8 array, enabling measurement of a network of 64 neurons invitro. The chip was post-processed to provide a bio-compatible gold interface between the electrodes and the neurons. Simulations and experimental results demonstrate the functionality of the new design. Additional measurements are underway to provide experimental confirmation of the system with in-vitro neurons.
Fabrication of Nanoscale Hydrophobic Regions on Anodic Alumina for Selective Adhesion of Biologic Molecules
Authors: Lin Xiefan , Ham Anthony S. W. , Villani Natalie A. , Lye Whye-Kei , Huang Qiyu , Lawrence Michael B. , Helmke Brian P. , Reed Michael L. 
Published: June 2019

AbstractStudies of selective adhesion of biological molecules provide a path for understanding fundamental cellular properties. A useful technique is to use patterned substrates, where the pattern of interest has the same length scale as the molecular bonding sites of a cell, in the tens of nanometer range. We employ electrochemical methods to grow anodic alumina, which has a naturally ordered pore structure (interpore spacing of 40 to 400 nm) controlled by the anodization potential. We have also developed methods to selectively fill the alumina pores with materials with contrasting properties. Gold, for example, is electrochemically plated into the pores, and the excess material is removed by backsputter etching. The result is a patterned surface with closely separated islands of Au, surrounded by hydrophilic alumina. The pore spacing, which is determined by fabrication parameters, is hypothesized to have a direct effect on the spatial density of adhesion sites. By attaching adhesive molecules to the Au islands, we are able to observe and study cell rolling and adhesion phenomena. Through the measurements it is possible to estimate the length scale of receptor clusters on the cell surface. This information is useful in understanding mechanisms of leukocytes adhesion to endothelial cells as well as the effect of adhesion molecules adaptation on transmission of extracellular forces. The method also has applications in tissue engineering, drug and gene delivery, cell signaling and biocompatibility design.
Monitoring of stem cell proliferation and differentiation using a permittivity-responsive biointerface
Authors: Bagnaninchi P.O. , Dikeakos M. , Veres T. , Tabrizian M. 
Published: June 2019

AbstractThe main approach of in-vitro bone engineering is based on the use of stem cells cultured in microporous scaffolds. In order to quickly and non-destructively assess the different steps of bone formation, we have proposed the use of a permittivity-responsive sensor to monitor the microporous scaffold, which in this instance acts as a biointerface. The aim of this study is to monitor and characterize the growth and differentiation of cells in the microporous biointerface through CP measurements. Measurements are performed throughout the entire process of the cells' culture, growth and differentiation using a dielectric probe and a vector network analyser under sterile conditions. This concept of a permittivity-responsive biointerface will lead to sensitive biosensors especially adapted for use in tissue engineering.
Oblique-Incidence Reflectivity Difference and Fluorescence Imaging of Oligonucleotide and IgG Protein Microarrays
Authors: Landry James P. , Zhu X. D. , Guo X. W. , Gregg J. P. 
Published: June 2019

AbstractWe have constructed an oblique-incidence reflectivity difference (OI-RD) microscope for fluorescent label-free imaging of DNA and protein microarrays on standard glass substrates. Using both OI-RD and fluorescence images, we demonstrate a difference in wetting behavior of labeled and unlabeled IgG protein molecules deposited on an aldehyde-derivatized glass surface. The potential of fluorescent labeling agents to influence the properties of proteins highlights the need for label-free microarray detection techniques to supplement existing fluorescence methods. We also present OI-RD images of an oligonucleotide microarray after printing and washing procedures to demonstrate the use of OI-RD for non-destructive monitoring of changes in the optical properties of microarrays during processing.
Quantum Dot Bioconjugates as Energy Donors in Fluorescence Resonance Energy Transfer Assays
Authors: Clapp Aaron R. , Medintz Igor L. , Matthew Mauro J. , Mattoussi Hedi 
Published: June 2019

AbstractLuminescent CdSe-ZnS core-shell quantum dot (QD) bioconjugates were used as energy donors in fluorescent resonance energy transfer (FRET) binding assays. The QDs were coated with saturating amounts of genetically engineered maltose binding protein (MBP) using a noncovalent immobilization process, and Cy3 organic dyes covalently attached at a specific sequence to MBP were used as energy acceptor molecules. Energy transfer efficiency was measured as a function of the MBP-Cy3/QD molar ratio for two different donor fluorescence emissions (different QD core sizes). Apparent donor-acceptor distances were determined from these FRET studies, and the measured distances are consistent with QD-protein conjugate dimensions previously determined from structural studies.
Structural and Initial Optical Characterization of Basalia Spicules in the Glass SpongeEuplectella
Authors: Sundar Vikram C. , Grazul John , Aizenberg Joanna 
Published: June 2019

AbstractWe report on the structural properties of siliceous spicules, found in the hexactinellid spongeEuplectella. Selective chemical etching ofEuplectellaspicules in bleach reveals the presence of a striated arrangement of silica spheres (∼50-200 nm in diameter) placed radially around a central, high-organic content cylindrical region. Complementary etching experiments with HF indicate a graded variation of silica content in these shells. The presence of such a multi-layered and variable-composition structure affords these spicules not only with enhanced structural integrity but could also be reflected in their optical properties. Qualitative, index-matched, refractive index measurements are shown to support this expectation.
Sea Urchin Mineralized Tissue
Authors: Stock S.R. , Ignatiev K. , Carlo F. De , Stock M.K. , Veis A. 
Published: June 2019

AbstractSea urchin ossicles are structural analogs of mammalian bones and serve as a model biomineral system. Sea urchins employ as wide a range of composite reinforcement strategies as are seen in engineering composites, and, studied as materials, teeth (and other ossicles) from different echinoid families illustrate combinations of reinforcement parameters and toughening mechanisms providing good functionality. Studying ossicles from different sea urchin families, therefore, is one method of probing the composite design space available to sea urchins, and this offers important guidance for engineering of structural tissue. This report is part of a larger multi-mode x-ray investigation employing microCT, both synchrotron and laboratory sources, phase contrast radiography and transmission microbeam diffraction mapping; voxels (volume elements) approaching 1 μm3can be interrogated noninvasively in millimeter sized samples. Only microCT results are presented below; these focus on sea urchin lanterns (jaw structure) and spines of a variety of sea urchin types and serve to illustrate how this sort of integrated approach might be applied to bone.
Formation of Complex Non-Equilibrium Morphologies of Calcite via Biomimetic Processing
Authors: Kim Yi-yeoun , Gower Laurie B. 
Published: June 2019

AbstractOur biomimetic approach for fabricating organic-inorganic composites with structures similar to biominerals is based on a novel mineralization process, called the Polymer-Induced-Liquid-Precursor (PILP) process. This process enables the deposition of non-equilibrium mineral morphologies of calcite under low-temperature and aqueous-based conditions [1], including patterned thin films of calcite. We have recently found that when a surplus of acidic polymer is added, the patterned mineral films act as a secondary template for directing new crystal outgrowths, which form into complex morphologies of calcite with time, such as fibrous mats and “horsetails”. Two interdependent factors, the polymer and Ca-ion concentration, which change the local solution environment over time, appear to modulate the creation of these different structures. Such observations may provide clues for unraveling the long-standing mystery of how biological systems fabricate their sophisticated and complex morphologies.
Colloidal Preparation of γ-Fe2O3@Au [core@shell] Nanoparticles
Authors: Fang Jiye , He Jibao , Shin Eun Young , Grimm Deborah , O'Connor Charles J. , Jun Moo-Jin 
Published: June 2019

Abstractγ-Fe2O3@Au core-shell nanoparticles were prepared through a combined route, in which high temperature organic solution synthesis and colloidal microemulsion techniques were successively applied. High magnification of TEM reveals the core-shell structure. The presence of Au on the surface of as-prepared particles is also confirmed by UV-Vis absorption. The magnetic core-shell nanoparticles offer a promising application in bio- and medical systems.
Peg-Containing Surfactants Enhance the Ultrasonic Permeabilizability of Liposomes
Authors: Lin Hung-Yin , Thomas James L. 
Published: June 2019

AbstractThe susceptibility of phosphatidylcholine liposomes to rupture by ultrasound was investigated. The liposomes were treated with (or had incorporated) a surface active dopant. The dopants studied here all contain polymers or oligomers of ethylene glycol as their hydrophilic “headgroup” component. All dopants strongly increased the ultrasonic permeabilizability of liposomes, as measured by the rate of release of a self-quenching fluorescent dye, at concentrations that caused no increase in permeability in the absence of ultrasound. The surface active dopants reached maximal effectiveness at about 1% of their critical micelle concentrations (CMCs). Using the roughly inverse relationship between CMC and membrane partition coefficient, we estimate that these maximally effective concentrations correspond approximately to the onset of headgroup contact among the surfactants in the membrane. Two surfactants, a PEG-lipid and a Pluronic triblock polymer, can be irreversibly incorporated into liposomes to give formulations that could in principle be used as drug delivery vehicles. The Pluronic polymer offers the possibility of additional temperature responsivity, owing to its highly temperaturedependent CMC.
Chromophore Binding to In-vitro Engineered Bio-mimetic Surfaces
Authors: Kinsella Joseph M. , Ivanisevic Albena 
Published: June 2019

AbstractThe research presented here aims to mimic the highly specialized local environment of the retina and to exploit the principles that govern its function, in order to construct functional optical interfaces that can be used as biotransducers. In the retina, a chromophore isomerizes and the protein to which it binds changes shape. In this proof-of-concept experiment we engineer an artificial surface to mimic the physiochemical environment of the retina and the key reaction of the visual cycle. We immobilized small peptides on silicon and assessed changes in their surface properties upon chromophore binding via AFM. Our observations suggest that when binding occurs it is accompanied by conformational changes of the surface-anchored peptide.
Poly-β-Cyclodextrins: Multifunctional Polymer Support for the Hydrolysis and Removal of Methyl Parathion
Authors: Lee Yongwoo , Singh Alok 
Published: June 2019

AbstractMicroparticles (32-53 μm) of cross-linked poly-β-Cyclodextrin (PCD) having a bifunctional hexyl spacer were prepared. PCD served as an insoluble robust matrix, which is chemically inert in acidic and basic media while preserving accessibility of pesticide methyl parathion (MPT) and its hydrolysis product p-nitrophenol (p-NP) to cyclodextrin cavities. The multi-utility of PCD was demonstrated as a stable biomaterial for adsorption of MPT and p-NP through inclusion phenomena and as a single unit system suitable for casting alternate enzyme/polyelectrolyte multilayers.
Biosynthesis of Silver Nanoparticles
Authors: Naik Rajesh R. , Stringer Sarah J. , Johnson Jay M. , Stone Morley O. 
Published: June 2019

AbstractThe use of biomolecules in the creation of inorganic materials offers an alternative to conventional synthetic methods. Biomolecules are currently used to control nucleation and growth of inorganic nanoparticles. Here we demonstrate the formation of silver nanoparticles in the presence of silver-binding peptides. Examination of the silver nanoparticles by transmission electron microscopy revealed a variety of crystal morphologies such as hexagons, triangles and spheres. The peptides serve to reduce the silver ions in the aqueous solution to metallic silver as well as control crystal growth. The nucleation property of peptides can be used as tool for bottom-up fabrication.