bluuebunny/crossref_metadata_2025_split huggingface dataset:
Piezoelectric polymers
Authors: Bauer Siegfried , Bauer-Gogonea Simona , Dansachmüller Mario , Dennler Gilles , Graz Ingrid , Kaltenbrunner Martin , Keplinger Christoph , Reiss Howard , Sariciftci Niyazi Serdar , Singh Thokchom Birendra , Schwödiauer Reinhard 
Published: April 2011

ABSTRACTThe science and technology of piezoelectric polymers has long been dominated by ferroelectric polymers from the polyvinylidene fluoride (PVDF) family. The piezoelectricity in this polymer class arises from the strong molecular dipoles within the polymer chain and from the resulting change of the dipole density upon application of a mechanical stimulus. Ferroelectric polymers show moderate piezoelectric coefficients (d33 and d31,32 around 20-30 pC/N) in comparison to ceramic piezoelectrics, with an acoustic impedance comparable to that of water. The thermal stability of the piezoelectric effect is limited to below 100°C, though stability up to 125°C has recently been announced. Applications of ferroelectric polymers emerged in many niches. A good example of a success story for PVDF applications are clamp-on transducers used as pressure sensor for Diesel injection lines, with selling numbers over 50 million pieces per year. A relatively new development are relaxor ferroelectric polymers, based on electron-irradiated poly(vinylidene fluoride) trifluoroethylene copolymers or on terpolymers of vinylidene fluoride, trifluoroethylene and chlorofluoroethylene. Relaxor ferroelectric copolymers exhibit strong electrostriction and thus large piezoelectric coefficients, when used under electric dc-bias fields. Internally charged cellular polymer foam electrets (ferroelectrets) resemble close similarities to ferroelectrics. They display large intrinsic piezoelectric d33-coefficients well above 100 pC/N and very small d31 and d32 coefficients, coupled with a limited thermal stability up to 50°C in the polypropylene workhorse material. The materials are pioneered in Finland and already entered the market in niches, for example in musical pick-ups. They promise large area applications, for example in surveillance and intruder systems. Finally, organic semiconductors have shown a rather unusual electromechanical response, governed by a power law S=V3/2 of strain S versus voltage V, located in between traditional piezoelectricity and electrostriction. The field of piezoelectric polymers therefore received new stimulus, and the material class of piezoelectric polymers has been significantly broadened recently.
Soft Actuators based on Polypyrrole and Polyaniline Composite Films
Authors: Kaneto Keiichi , Takashima Wataru 
Published: April 2011

ABSTRACTElongation and contraction of polypyrrole and poly(3-methoxyaniline-5-sulfonate) (PMAS) composite films induced upon electrochemical oxidation and reduction, viz., electrochemomechanical deformation (ECMD) are studied. The composite films were electrochemically prepared in electrolyte solutions of pyrrole and dodecylbenzene sulfonic (DBS) acid with a presence of PMAS acid. The contents of DBS and PMAS were varied. Films which were obtained at higher contents of PMAS, were gel like due to a lot of water content. The change of film length due to ECMD was measured as functions of various electrolytes in either aqueous or organic solvents. The results indicated that films exhibited both cathodic and anodic expansions depending on the bulkiness of cations and anions as well as the content of PMAS.
Non-linear charge transport in polythiophene under high AC field
Authors: Obrzut Jan , Psurek Tatiana , Chiang C. K. , DeLongchamp Dean M. 
Published: April 2011

ABSTRACTComplex impedance and conductivity were measured for regioregular poly(3-hexylthiophene) (P3HT) at alternating current (AC) voltages using a waveform technique. The waveforms were Fourier transformed from time domain to frequency domain and analyzed at fundamental and higher order harmonic frequencies. It was found that the impedance of the semi-conducting P3HT decreases with increasing electric field strength. The non-linear charge transport is dominated by a third harmonic response that originates from extended polarizability of π-type electronic states. The third order non-linear conductivity can be used to quantify the effect of an electric field on the conduction mechanism and to correlate the intrinsic charge carriers mobility with molecular structure.
Symmetry reduction of δ-plutonium: an electronic-structure effect
Authors: Moore Kevin T. , Söderlind Per , Schwartz Adam J. , Laughlin David 
Published: April 2011

AbstractUsing first-principles density-functional theory calculations, we show that the anomalously large anisotropy of δ-plutonium is a consequence of greatly varying bond-strengths between the 12 nearest neighbors. Employing the calculated bond strengths, we expand the tenants of classical crystallography by incorporating anisotropy of chemical bonds, which yields a structure with the monoclinic space groupCmfor δ-plutonium rather than face-centered cubicFm3m. The reduced space group for δ-plutonium enlightens why the ground state of the metal is monoclinic, why distortions of the metal are viable, and has considerable implications for the behavior of the material as it ages. These results illustrate how an expansion of classical crystallography that accounts for anisotropic electronic structure can explain complicated materials in a novel way.
Statistical Texture Analysis of Microscopy Images for the Purpose of Surface Characterization
Authors: Sadowski Thomas E , Broadbridge Christine Caragianis , DaPonte John 
Published: April 2011

AbstractThis study focuses on the application of an image processing technique known as texture analysis to provide a complementary method to process non-contact atomic force microscopy data. For the current study, SrBi2Ta9O9 (SBT) thin films (∼200nm) on silicon samples were prepared via MOD and imaged via nc-AFM. Previous studies have qualitatively chosen grain size or grain density to quantify the surface characteristics of SBT but for this study texture analysis was used. Results obtained from the texture analysis and the subsequent stepwise discriminant analysis illustrated the importance of grain density and its effect on the statistics obtained from the gray scale cooccurrence matrix.
Combinatorial Methodology on Zeolite Membrane Development for Organic Chemical Process Intensification
Authors: Inoue Tomoya , Hasegawa Yasuhisa , Nagase Takako , Kiyozumi Yoshimichi , Hamakawa Satoshi , Mizukami Fujio 
Published: April 2011

AbstractCombinatorial methodology for zeolite membrane development is discussed. Zeolite membrane is now attracting attentions as an energy-saving separation apparatus via pervaporation and/or vapor permeation, but sometimes it suffers performance (flux and/or separation factor) deterioration due to lack of chemical stability. We separate the development scheme into three steps – i) zeolite selection via chemical affinity and stability evaluation in powder applying combinatorial methodology, ii) membrane preparation for thus selected zeolite species, and iii) their evaluation in parallel manner. We have successfully developed hydrophilic zeolite membranes with tolerance against acidic environment. Thus developed zeolite membranes were successfully applied esterification reaction from a stoichiometric mixture of a carboxylic acid and an alcohol by assisting equilibrium shift via direct pervaporation from crude reaction solution.
Biocatalytic Activity of Polyethylene Imine Hydrogel Complexes with Transition Metal Ions
Authors: Bektenova Gulnara , Chinibayeva Nurzhan , Bekturov Essen 
Published: April 2011

AbstractPolyethylene imine hydrogel complexes with various salts of ferric and ferrous iron and also with complex salts of iron as well as insoluble ternary complexes of various composition: low cross-linked polyethylene imine hydrogel - copper (II) nitrate - sodium dodecylbenzylsulfate have been received. Their biocatalytic properties in the reaction of hydrogen peroxide decomposition (catalase activity) have been investigated. It was shown that catalase activity of complexes depends on the salts type and valence state of iron ions. The complexes of ferric iron as well as ternary complexes are most active in the reaction of hydrogen peroxide decomposition.
The fabrication of hydrogel as a microvalve in microfluidic system
Authors: Wei Chehung , Chen Jui-Hung 
Published: April 2011

AbstractThe small volume of sample and fast response time are the primary features of micro fluidic system. It is essential for expensive samples. Microvalve is a key to regulate the flow movement component in an integrated microfluidic system. The working principle of conventional microvalves relies on its mechanical or electromagnetic properties. These valves are neither biocompatible nor are suitable for bioassays. Stimuli-response hydrogels whose properties of efficient mode of energy conversion (chemical to mechanical), excellent biocompatibility and the combination of multiple function (sensing and actuation) have become the leading candidate as engineered microscale components. In this paper, we study the feasibility of thermo-sensitive hydrogel as a valve on the microchip. A metal resistor was used as the temperature regulator. The results show that the miniaturization fabrication of the hydrogel depends on many factors like the volume of the hydrogel (the size of the valve), the vacuum condition (the evaporation rate) and the deposition substrate. The degree of swelling and deswelling of the hydrogel valve depends on the size of the hydrogel. This micro fluidic system is regulated by temperature change of the aqueous solution. The integration with other fluidic component is crucial for practical application.
Water Mobility in Reverse Micelles Studied by Quasielastic Neutron Scattering and Molecular Dynamics Simulation
Authors: Ladanyi Branka , Levinger Nancy 
Published: April 2011

AbstractReverse micelles (RMs) are aggregates in which nanoscale droplets of a polar liquid, usually water, are surrounded by a surfactant layer in a nonpolar continuous phase. They are widely used as media for reactions in which the extent of confinement or the presence of a surfactant interface play a central role. We have used molecular dynamics (MD) computer simulation and quasielastic neutron scattering (QENS) and to investigate the mobility of water molecules in reverse micelles. The contribution of water to the QENS signal is enhanced by deuterating the surfactant and the nonpolar phase. Our studies of water mobility have focused on the effects of water pool size, determined by the water/surfactant mole ratios w0, as well as on the properties of the water-surfactant interface. Specifically, we have examined the effects of varying w0 and of substituting other alkali ions for the usual Na+ counterion of the anionic surfactant AOT (bis (2-ethylhexyl) sulfosuccinate)). We find good agreement between the QENS signal and its prediction from MD simulation. This allows us to obtain additional insight into water mobility by analyzing the MD self-intermediate scattering function (ISF) of water hydrogens in terms of contributions from molecular rotation and translation and from molecules in different interfacial layers. MD data indicate that the translational ISF decays nonexponentially due to lower water mobility close to the interface and to confinement-induced restrictions on the range of translational displacements. Rotational relaxation also exhibits nonexponential decay. However, rotational mobility of O-H bond vectors in the interfacial region remains fairly high due to the lower density of water-water hydrogen bonds in the vicinity of the interface.
Chemically Selective Reactions in Confined Spaces in Hybrid Aerogels
Authors: Liu Xipeng , Yao Chunhua , Risen William M 
Published: April 2011

AbstractBy employing novel hybrid silica/functional polymer aerogels, control of the course of chemical reactions between reactants confined inside of the aerogels with reactants whose access to the confinement domain is controlled by diffusion has been explored. Thus, monolithic silica/biopolymer hybrid aerogels have been synthesized with coordinated metal ions that can react with amino acids, such as L-cysteine, that are provided externally in a surrounding solution. Metal ions, such as Au(III), that can react in solution with the amino acid to produce one set of products under a given set of stoichiometric or concentration conditions, and a different set of products under a second set of conditions, were selected for incorporation into the aerogel. It was discovered that the course of the reaction can be changed by spatial confinement of the reaction domain in the aerogel. For example, in the case of Au(III) and L-cysteine, the Au(III) ions are confined in nanoscale domains, and when they are reacted with the amino acid, the nature of the reaction products is controlled by diffusion of the L-cysteine into the domains. Exploration of these and related phenomena will be presented.
Molecular Dynamics Studies of Surface Nucleation and Crystal Growth of Si on SiO2Substrates
Authors: Lee Byoung-Min , Baik Hong Koo , Kuranaga Takahide , Munetoh Shinji , Motooka Teruaki 
Published: April 2011

AbstractMolecular dynamics (MD) simulations of atomistic processes of nucleation and crystal growth of silicon (Si) on SiO2substrate have been performed using the Tersoff potential based on a combination of Langevin and Newton equations. A new set of potential parameters was used to calculate the interatomic forces of Si and oxygen (O) atoms. It was found that the (111) plane of the Si nuclei formed at the surface was predominantly parallel to the surface of MD cell. The values surface energy for (100), (110), and (111) planes of Si at 77 K were calculated to be 2.27, 1.52, and 1.20 J/m2, respectively. This result suggests that, the nucleation leads to a preferred (111) orientation in the poly-Si thin film at the surface, driven by the lower surface energy.
Chemical bath deposition of nanocrystaline CdS and CdPbS layers and investigation of their photoconductivity
Authors: Rakovics Vilmos 
Published: April 2011

ABSTRACTThe investigation of photoconductive properties of chemical bath deposited (CBD) cadmium sulphide (CdS) layers was the main objective of this work. For completeness, the CdS layers were characterized using X-ray diffraction, scanning electron microscopy, optical absorption, DC electrical conductivity, photoconductivity measurements. It has been found that the CdS layers grown are hexagonal with (002) preferential orientation. The n-type CdS materials show 100–200 nm clusters consisting of 10–20 nm size crystallites. The optical band gap is 2.42-2.52 eV, which shows a red-shift to 2.34 eV upon heat treatment. The effect of Cu doping and co-deposition of CdS with PbS were also investigated. Dark conductivity was increased after heat treatment of pure CdS layers, and decreased in case of Cu doped samples. Photoconductive response time of Cu doped CdS and Cd(Pb)S samples were smaller than the response time of pure CdS samples.
Surface Enhanced Raman Scattering on Physically Self-assembled Ag Nanorod Arrays
Authors: Suzuki Motofumi , Maekita Wataru , Wada Yoshinori , Nakajima Kaoru , Kimura Kenji , Fukuoka Takao , Mori Yasushige 
Published: April 2011

ABSTRACTWe have established a process to fabricate Ag nanorod arrays with tunable morphology, hence tunable plasmonic properties. Based on a dynamic oblique deposition (DOD) technique, the nanorods are aligned in a way where their major axis is quasi-parallel. The aspect ratio of the nanorods is adjusted by choosing an appropriate DOD condition to show plasma resonance in the wavelength region around the Raman scattering at the excitation wavelength of 785 nm. The nanorod arrays thus tuned provide intense surface enhanced Raman scattering useful for practical applications to biochemical sensors.
Functionalization of 3-D Structures for Grafting of Biological Molecules
Authors: Oillic Cécile , Mur Pierre , Blanquet Elisabeth , Delapierre Guillaume , Vinet Françise , Billon Thierry 
Published: April 2011

ABSTRACTEven though most microarrays present good quality, accuracy and reliability, they are made on a planar surface structure, which neither enough increases the accessibility of the targets to the probes nor the loading capacity of the solid support. To achieve a high density of reactive functions, the use of a non-planar structure is investigated to increase the available surface area for grafting of biomolecules. We propose to build up a pseudo-three-dimensional silicon structure, covered with a specific oxide layer, and then functionalized, allowing to introduce covalent and stable bindings of amino-modified oligonucleotides probes on the reactive layer of the support. The performances of these supports after silanisation are investigated by means of hybridization experiments using complementary fluorescent labeled-oligonucleotides targets. Our results indicate that these novel surfaces provide a higher specific surface area for attaching biomolecules and higher accessibility of the targets, which will increase the density of biomolecules and hence, the sensitivity of the fluorescence signal in comparison to the results obtained with a planar surface structure.
Catalysis with Transition Metal Nanoparticles of Different Shapes
Authors: Narayanan Radha , El-Sayed Mostafa A. 
Published: April 2011

ABSTRACTColloidal metal nanoparticles have a high surface-to-volume ratio which makes them potentially attractive catalysts. Furthermore, atoms located at different facets, edges, or corners could show different catalytic activity. For this reason, different shapes could have different catalytic activities. In addition, surface atoms are so active that there could be significant changes in their shape and size during the course of nanocatalysis. As a result, a thorough examination on the effect of the catalytic process on the shape and size of colloidal metal nanoparticles after catalysis is necessary to fully evaluate their use in catalytic processes.In this paper, we briefly review our recent work on examining the shape dependence of nanocatalysis as well as the stability of platinum and palladium nanoparticles during the course of two reactions: the electron transfer reaction and the Suzuki reaction. It is found that nanocatalysis is indeed shape-dependent during the early stages of the electron transfer reaction. During the full course of the reaction, there are changes in the nanoparticle shape as well as changes in the activation energy that takes place. In the case of a relatively harsh reaction such as the Suzuki reaction, spherical palladium nanoparticles grow in size due to Ostwald ripening processes. Tetrahedral platinum nanoparticles catalyzing the Suzuki reaction transform into spherical shape and grow larger in size. We also conducted studies on the effect of individual reactants on the nanoparticle size and shape. In addition, the surface catalytic mechanisms of the reactions have been confirmed using spectroscopic tools such as FTIR and Raman spectroscopy. These kinds of studies will be very useful in the process of designing better nanocatalysts in the future.
Integration of Nanoparticles Into and Onto Optical Fiber Sensors
Authors: Dhawan A. , Muth J. F. 
Published: April 2011

ABSTRACTMetallic and semi-conducting nano-particles were incorporated into and on the surface of optical fibers to form sensors and other optoelectronic devices on standard telecommunications grade optical fibers. Optical fibers provide a macroscopic platform to exploit the wide range of functionality inherent in nanostructures and nano-particles. Several ways of forming sensitive and robust chemical sensors, based on plasmon resonances of metallic islands and nano-particles, were demonstrated. These nano-particles were formed on tip or surface of the optical fibers by thermal or plasma arc annealing of very thin (4 -12 nm) gold films, that were deposited by electron beam deposition and sputtering. Development of in-line optical fiber structures, involving single mode or multimode optical fibers fused to an arrangement of coreless and graded index fibers, was also carried out. This enabled light propagating in the core of the optical fiber to expand to the surface of the coreless fiber and to effectively interact with nano-particles on the surface and the environment. Metallic and semiconducting nano-particles were also incorporated inside an optical fiber matrix and this could enable us to effectively characterize novel materials and possibly form optical switches. Moreover, these optical fiber sensors and devices were integrated into textile structures to explore the possibility of formation of optoelectronic textiles.
Surface Characterization of Silicon Carbide Following Shallow Implantation of Palladium Ions
Authors: Muntele Claudiu I. , Sarkisov Sergey , Muntele Iulia , Ila Daryush 
Published: April 2011

ABSTRACTSilicon carbide is a promising wide-bandgap semiconductor intended for use in fabrication of high temperature, high power, and fast switching microelectronics components running without cooling. For hydrogen sensing applications, silicon carbide is generally used in conjunction with either palladium or platinum, both of them being good catalysts for hydrogen. Here we are reporting on the temperature-dependent surface morphology and depth profile modifications of Au, Ti, and W electrical contacts deposited on silicon carbide substrates implanted with 20 keV Pd ions.
Effects of Possible Spin-Spin Interactions on EPR spectra of Cu2+ exchanged Faujasite–X (I)
Authors: Kowenje Chrispin B. O. , Jones Barry R. , Kanyi Charles W. 
Published: April 2011

ABSTRACTThe interpretation of the continuous wave electron paramagnetic resonance (CW-EPR) spectra of Cu2+ exchanged in Faujasite zeolite is not straightforward. Recent literature points to the role of both Cu2+ zeolite sites and Cu2+ relationship to lattice Al in determining the parameters of Cu2+ spin Hamiltonian. Our work shows that at low concentration, Cu2+ EPR signals show negligible spin-spin interactions. At higher Cu (II) concentrations, a third CW-EPR spectrum that has contributions from both the CW-EPR and the spin-spin interactions, appears.
Ion Modification for Improvement of Electrical Properties of Perovskite-based Ferroelectric Thin Films Fabricated by Chemical Solution Deposition Method
Authors: Uchida Hiroshi , Yasui Shintaro , Ueno Risako , Nakaki Hiroshi , Nishida Ken , Osada Minoru , Funakubo Hiroshi , Katoda Takashi , Koda Seiichiro 
Published: April 2011

AbstractIon modification for various perovskite-based ferroelectric thin films using rare-earth cations was attempted for improving the electrical properties. Strategy for controlling the electrical properties is mainly based on two concepts, that is, (i) substituting the volatile cations such as Pb2+ and Bi3+, and (ii) controlling the crystal anisotropy of perovskite unit cell. In this study, the influences of ion-modification conditions (i.e., amount, species and occupying site of substituent cations) on the electrical properties of perovskite-based ferroelectric films fabricated by a chemical solution deposition were investigated. Substituting volatile cations in simple-perovskite oxides, such Pb2+ in Pb(Zr,Ti)O3 and Bi3+ in BiFeO3, for the rare-earth cations like La3+ and Nd3+ reduced the leakage current density of these films due to suppressing the metal and / or oxygen vacancies, as well as in layered-perovskite oxides, such as Bi4Ti3O12 films [i.e., strategy (i)]. Also, crystal anisotropy of perovskite-based oxides could controlled by varying the species and the occupying site of substituent cations [i.e., strategy (ii)]; for example, the crystal anisotropy of Pb(Zr,Ti)O3 lattice was elongated by Ti- and Zr-site (B-site) substitution using rare-earth cations whose ionic radii locate on the smaller part of rare-earth series (such as Y3+, Dy3+), that resulted in enhancing the spontaneous polarization. We concluded that the strategy for controlling the electrical property mentioned in this study would be applicable for a various kind of perovskite-based ferroelectric films.