bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Nanotube-on-Insulator (NOI) Approach toward Single-Walled Carbon Nanotube Devices
Authors: Liu Xiaolei , Han Song , Zhang Daihua , Ryu Koungmin , Zhou Chongwu
Published: April 2011

We present a novel nanotube-on-insulator (NOI) approach to produce high-yield nanotube devices based on aligned single-walled carbon nanotubes. First, we managed to grow aligned nanotube arrays with controlled density on crystalline, insulating sapphire substrates, which bear analogy to industry-adopted silicon-on-insulator substrates. Based on the nanotube arrays, we demonstrated registration-free fabrication of both top-gated and polymer-electrolyte-gated field-effect transistors with minimized parasitic capacitance. In addition, we have successfully developed a way to transfer these aligned nanotube arrays to flexible substrates. Our approach has great potential for high-density, large-scale integrated systems based on carbon nanotubes for both micro- and flexible electronics.
Solution-Processed Hybrid Polymer-Quantum Dot Nanocomposite for Infrared Photodetection and Photorefractivity
Authors: Choudhury Kaushik Roy , Kim Won Jin , Sahoo Yudhisthira , Lee Kwang-Sup , Prasad Paras N.
Published: April 2011

Successful integration of solution-processible nanocrystal quantum dots, active over a wide spectral range in the infrared, organic molecules and polymers, to fabricate efficient photoconductive and photorefractive devices operational at important optical communication wavelengths is achieved. Sensitization of the polymeric composites by quantum dots led to high photocurrents at 1340 nm, yielding a high photoconductive quantum efficiency. In the photorefractive composites, pronounced two-beam coupling was observed, leading to good optical gains achievable by low-power continuous-wave illumination. The photoresponse was further extended to 1550 nm. A steady state diffraction efficiency was obtained in the dynamic refractive-index gratings with appreciable response times. In order to enhance the photoconductive performance of the devices, the organic semiconductor pentacene was incorporated into the hybrid composite through a soluble presursor. At the operating wavelength of 1340 nm, the photocurrent increased significantly as the amount of pentacene in the composite was increased, resulting in a spectacular improvement of external quantum efficiency.
The Preparation and Characterization of a Novolac Cured Epoxy-Clay Nanocomposites
Authors: Tsai Tsung-Yen , Lu Shau-Tai , Li Chih-Hung , Huang Chin-Jei , Chen Li-Chun , Liu Jia-Xiang
Published: April 2011

Intercalated or exfoliated nanocomposites were composed by the novolac cured epoxy and one of three different kinds of layered silicates, such as montmorillonite (PK-802), saponite (Semecton-SA) and nontronite (PK-805). The bi-functional modifiers (PI/BEN or MI/BEN) with different ratio, which contained one of the promoters (2-phenylimidazole, PI and 2-methylimidazole, MI) of epoxy and benzalkonium chloride (BEN), were intercalated into the gallery regions of pure clays at the same time and followed by a crosslinking reaction. The properties of novolac cured epoxy/clay nanocomposites were characterized by wild-angle X-ray diffraction (WAXRD), thermal analysis (TGA/DSC), coefficiency of thermal expansion (TMA), mechanical properties (DMA), and transmission electron microscopy (TEM). According to the measurement, these novolac cured epoxy-clay nanocomposites have shown the significant improvement in the thermal, mechanical and barrier properties.
Effect of Silica-Nanoparticle Dispersion on Holographic Recording in Methacrylate-Based Photopolymer Films
Authors: Takahashi Hiroshi , Naitoh Takahiro , Tomita Yasuo
Published: April 2011

Transmission volume holograms recorded in two types of methacrylate-based photopolymer films that include benzyl n-butyl phthalate (BBP) or Poly(methyl methacrylate) (PMMA) are studied. It is shown that both BBP and PMMA molecules can be uniformly dispersed into methacrylate monomers and that a refractive index modulation as high as ∼0.005 is recorded by optimizing their volume concentrations. Moreover, it is also shown that the additional doping of silica nanoparticles substantially suppresses polymerization shrinkage without increasing optical scattering loss.
Modeling the fs Demagnetization: Laser-Induced Reversal in an Applied Magnetic Field
Authors: Longa Francesco Dalla , Boesten Dion , Kicken Harm H.J.E. , de Jonge Wim J.M. , Koopmans Bert
Published: April 2011

A novel model for ultrafast laser-induced magnetization dynamics is analyzed. Equilibration of the magnetic system is described by including electron-phonon scattering events with a finite spin flip probability. Recently, we demonstrated that such a model predicts a direct relation between the demagnetization time and the Gilbert damping. Here we present numerical simulations based on the same Hamiltonian, but including the presence of an external applied field. Thereby, reversal of the magnetization after heating above the Curie temperature (Tc) can be modeled. We demonstrate that magnetization reversal can be achieved even if the lattice temperature stays below Tc.
Metal-insulator Transition and Magnetic Domains in (Ga,Mn)As Epilayers
Authors: Dourlat Alexandre , Gourdon Catherine , Jeudy Vincent , Bernardot Frédéric , Testelin Christophe , Lacaze Emmanuelle , Thevenard Laura , Mauguin Olivia , Largeau Ludovic , Patriarche Gilles , Lemaître Aristide
Published: April 2011

We investigate the magnetic domain pattern in (Ga,Mn)As epilayers with perpendicular magnetic anisotropy. We show that post-growth annealing, besides improving the magnetic and transport properties, also drastically changes the domain pattern. Strong pinning of domain walls along the <110> directions is suppressed and large-size domains are observed.
Above Room-Temperature Ferromagnetism in GaN Powders by Calcinations with CuO
Authors: Noice Lori , Seipel Bjoern , Erni Rolf , Gupta Amita , Li Chunfei , Moeck peter , Rao Venkat , Browning Nigel
Published: April 2011

Gallium nitride powders were calcined with copper oxide in either air or N2 and analyzed by means of powder X-ray diffraction (XRD), high-resolution parallel illumination (HRTEM) and scanning probe transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS) in order to address the structural and electronic effects of Cu-incorporation into GaN. Gallium oxide and multiple copper oxide phases corresponding to the calcination environment were detected. Significant changes in the lattice parameters and electronic structure of the N2-processed GaN indicate incorporation of both copper and oxygen into the GaN lattice as well as changes in the chemical bonding due to the calcinations process. SQUID magnetometer measurements at 300 K demonstrated ferromagnetism in selected samples.
Nanoscale Indentation of Polymer and Composite Particles by Atomic Force Microscopy
Authors: Armini Silvia , Vakarelski Ivan U. , Whelan Caroline M. , Maex Karen , Higashitani Ko
Published: April 2011

Atomic Force Microscopy (AFM) was employed to probe the mechanical properties of surface-charged polymethylmethacrylate (PMMA)-based terpolymer and a composite terpolymer core-silica shell nanosphere in air and water media. Since these materials exhibit enhanced mechanical properties, such as toughness and elasticity, and enhanced chemical stability, they are particularly interesting for potential applications in reducing defectivity during the process of Chemical Mechanical Planarization. The polymer particles were subjected to a thermal treatment aimed at improving their mechanical properties in terms of hardness (H) and elastic modulus (E). By analysis of force-displacement curves and on the basis of Hertz's theory of contact mechanics, Young's moduli were measured for the terpolymer compared with the composite that has expected mechanical property enhancement due to its silica shell. In air, E increases from 4.3 GPa to 6.6 GPa for the treated terpolymer compared with the respective value of 10.3 GPa measured for the composite. In water, E increases from 1.6 GPa to 4.5 GPa for the thermally treated terpolymer that is comparable with the respective value of 3.6 GPa measured for the composite. This observation suggests that as an alternative to the creation of polymer-silica composite nanoparticles for CMP, comparable mechanical properties can be achieved by a simple heat treatment step.
Interaction Forces Between Thermoresponsive Surface and Colloidal Particle in Aqueous Solution Studied Using Atomic Force Microscopy
Authors: Ishida Naoyuki , Kobayashi Mikio
Published: April 2011

The interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using an atomic force microscope (AFM). Measurements were conducted between a smooth silicon wafer on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Below the lower critical solution temperature (LCST) of PNIPAAm, there were large repulsive forces between the surfaces, while attractive forces were observed above LCST. When surface hydrophobicity of the particles increased, the magnitude of attractive force tended to increase. The changes of hydration state of the grafted PNIPAAm chains depending on temperature is considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and the hydrophobic particles in the interaction forces is discussed.
A Novel Approach for the Preparation of InP Nanocrystals
Authors: Sun Zhaoyong , Zhang Jun , Zhang Ming , Fang Jiye
Published: April 2011

III-V semiconductor nanocrystals are of considerable interest due to their extensive applications in the optoelectronic and biomedical fields. In order to meet the practical use, the convenient and scalable production of III-V narrow-disperse nanocrystals is inspiring. We report an efficient and rapid method of preparing highly monodisperse InP nanocrystals using a wet-chemical redox synthetic approach with a noncoordinating solvent, employing organic reducing agent LiBH(CH2CH3)3 and yellow phosphor. As advantages of this approach, reaction temperature is relatively low (80°C-120°C) and reaction time is less than 2 hours. Our characterization shows that the photoluminescence properties of InP nanocrystals are highly dependent on the particle size.
On the Structural and Optical Properties of ZnO Nanoparticles Formed in Silica by Ion Implantation
Authors: Tagliente Maria Antonella , Massaro Marcello , Mattei Giovanni , Mazzoldi Paolo , Pellegrini Giovanni , Bello Valentina , Carbone Daniela
Published: April 2011

Zinc Oxide (ZnO) is a II-VI semiconductor material with a wide direct band-gap of 3.37 eV at room temperature (RT). In the past decades, the material has been used for a variety of applications such as gas sensors, surface acoustic wave devices, or transparent contacts. Recently, ZnO has gained a new substantial interest primarily because to its potentialities for optoelectronic and spintronic applications. The renewed interest has been fueled by the availability of high-quality bulk substrates, reports of p-type conduction and theoretical predictions of its ferromagnetic behavior at room temperature when doped with transition metals. In the domain of optoelectronics, its main applications include devices emitting in the blue and UV regions by exploiting its wide band-gap such as light-emitting and laser diodes. With respect to several wide band-gap semiconductor materials, ZnO has the advantage of a larger exciton binding energy (about 60 meV) which paves the way for an intense near-band-edge excitonic emission at room and higher temperatures. On the other hand, a band gap engineering can be also achieved by the incorporation of Cadmium and Magnesium atoms into the ZnO lattice.

Many techniques have been used to prepare ZnO in various forms, such as single crystals, powders and films. In the past few years, the great attention toward materials with nanometric size have motivated a number of studies on the synthesis of ZnO nanocrystals. Ion implantation is one of the most effective and versatile technique to obtain nanoparticles. ZnO particles embedded in silica matrix have been successfully prepared by ion implantation followed by thermal oxidation.

In this work, we report on a detailed structural and optical characterization of the ZnO-silica nanocomposites by using several complementary techniques; in particular, Glancing Incidence X-ray Diffraction (GIXRD), Rutherford Backscattering Spectrometry (RBS), linear Optical Absorption (OA) in the UV-near IR spectrum and Photo-Luminescence (PL). The ZnO nanoparticles embedded in SiO2matrix were prepared by implanting the substrates with 130 keV Zn+ions at doses of 1, 1.5 and 2´1017 ions/cm2. Subsequently, the implanted samples were annealed for 1h in a furnace at a temperature between 500 and 800°C under flowing O2 gas. X-ray diffraction results indicate the formation of Zn and ZnO nanoparticles in the as-implanted and annealed samples, respectively. Moreover, the ZnO nanocrystals embedded in the SiO2matrix have a (002) preferred orientation. After the oxidation, the optical absorption spectra show an absorption edge at about 374 nm by confirming the presence of the ZnO particles. A relatively strong exciton photoluminescence peak was observed at room temperature under pulsed N2 laser excitation at l=337nm. The results obtained, peculiarly related to the implantation doses and annealing temperature, are discussed.
Patterning of Cell Attachment to Biocompatible Glassy Polymeric Carbon by Silver Ion Implantation
Authors: Zimmerman Robert Lee , Gurhan Ismet , Ila Daryush , Ozdal-Kurt F. , Sen B. H. , Rodrigues M.
Published: April 2011

Although Glassy Polymeric Carbon (GPC) is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve. There is concern that the tissue lose adhesion and create the condition for embolisms downstream. We have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in GPC can completely inhibit cell attachment on implanted areas while leaving adjacent areas unaffected. Patterned ion implantation permits precise control of tissue growth on medical applications of GPC.
Design and Synthesis of a Multifunctional Probe for Bio-Imaging and Therapeutics
Authors: Liu Yu-San , Liang Chi Hui , Vernier P. Thomas , Sun Yinghua , Gundersen Martin A.
Published: April 2011

We report the synthesis of CdSe/ZnSe/ZnS (core/shell/shell) quantum dots (QDs) as a fluorescence probe for biological cells, and their functionalization with carbon nanotube (CNT)-retrovirus complexes (labeled with the QDs) to form multi-functional tool with potential applications for cancer therapeutics. A mild method for preparing this QD-CNT-retrovirus complex, which preserves viral function, is reported. Observations and imaging under fluorescence confocal microscope show the expression of enhanced green fluorescent protein (EGFP) gene and QD uptake in viable cells, indicating that this novel probe is able to enter cells, crossing the natural barrier of the cell membranes. Such multi-functional probes have potential as medical diagnostics and for therapeutics for diseases including cancer. The multifunctional probe is of interest for potentially broad applications – with the quantum dots as the visualization aid, carbon nanotubes as an efficient opto-thermo converter for selective extermination of cells with the help of light irradiation at near-IR range, and the retrovirus as a vehicle for genetic therapy.
Microhydraulic Actuation Using Biological Ion Transporters Reconstituted on Artificial BLM
Authors: Sundaresan Vishnu Baba , Leo Donald J
Published: April 2011

Plants and animals have the natural ability to exhibit force through controlled pressurization of cellular compartments. The mechanism through which force is generated is powered by biological fuels. The process involves moving ions against an established concentration gradient expending free energy from bio-fuels like Adenosine-tri-phosphate (ATP), kinesin etc., Materials exhibiting deformation using biological processes are called Nastic materials. The functional component in mass transfer across the cell boundary is the ion transporter embedded in cell membranes. The ion transporters which are complex protein molecules, move ions and water molecules for an applied chemical or electrical stimulus. The bio-inspired microhydraulic actuator uses the same functional component in plant cells reconstituted on a planar bilayer lipid membrane (BLM) formed from purified lipids. The protein transporters pump ions and fluid into an enclosed cavity to cause deformation. The controlled fluid transport through AtSUT4(proton-sucrose co-transporter extracted from Arabidopsis thaliana) reconstituted on a 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) BLM on porous lead silicate glass plate driven by a proton gradient demonstrated the ability to move fluid across the membrane. This article discusses a prototype microhydraulic actuator that increases in thickness for an applied pH and sucrose concentration gradient.
Observation of Leggett's Mode in Mg1-xAlxB2
Authors: Ponomarev Yaroslav , Kuzmichev Svetoslav , Mikheev Mikhail , Sudakova Marina , Tchesnokov Sergei , Bulychev Boris , Maksimov Evgenii , Krasnosvobodtsev Sergei
Published: April 2011

A detailed investigation of multiband superconductivity and Leggett's collective mode in the Mg1-xAlxB2 system was carried out using tunneling and Andreev spectroscopy
Electrical Devices Obtained From Polymeric Precursors Process
Authors: Carvalho Claudio Luiz , Peruzzi Raphael Otavio , Solano Rudi A. V.
Published: April 2011

Nowadays, many investments have been made in the area of superconductor materials, with the aim to improve theirs potential technological applications. Applications on the energy transport using cables, to get high resolution images in the medicine use high magnetic fields, high speed signals use superconductor devices all of them are in crescent evidence and they are showing that the future is coming and next for this new kind of materials. Obviously that everything of this is possible due to the increasing of research with new materials, where the synthesis, characterization and applications are of the mainly objective of these researches. The production of cable for the energy transport has been in advanced stage as the bulks production is too. However, the film production that to aim at the electronic devices area are not so developed or its still need expensive investments. Thinking about that, we are developing a research where we may increase the relation of cost/benefits. Thereby, we are applying the polymeric precursors method to obtain films that will be used in the built of electronic devices. Thin films (mono and multilayers, on crystalline or metallic substrates, controlled thickness) of the BSCCO system have been obtained from dip coating deposition process with excellent results in terms of preferential orientation, controlled thickness, large area, what may indicate future applications.

Based on these results, we present an electrical circuit and their principal characteristics as superconductor transition (85K), transport current density and structure. DC four probes method, scanning electron microscopy, digital optical microscopy, X-ray diffractometry were some techniques used for the characterization of this superconductor electric device.
Investigation of In-Field Properties of YBCO Film with Artificial Pinning Centers
Authors: Kobayashi Hiroyoshi , Ishida Satoru , Takahashi Kazuhiro , Konishi Masaya , Ibi Akira , Miyata Seiki , Yamada Yutaka , Shiohara Yuh , Kato Takeharu , Hirayama Tsukasa
Published: April 2011

We have investigated the thickness dependence of critical current for YBa2Cu3O7-x (YBCO) film with artificial pinning centers on metallic substrate. Artificial pinning centers were introduced by the pulsed laser deposition (PLD) using YBCO target including YSZ particles. The film over 1 μm in thickness exhibited with high critical current (Ic) of 40.7A in applied magnetic field of 3T parallel to the c-axis at 77K. This value was 5 times as high as the normal YBCO film without artificial pinning centers. The large Ic enabled us to approach to a practical application in the near future. Furthermore, it was clarified that the columnar nano-structure formed in the film, we call “the bamboo structure”, was a dominant pinning center because each Jc-θ curve of all thick films formed a universal line by the normalization of Jc. In addition, it was also found that YSZ addition has an optimal concentration for pinning by the study of YSZ concentration in the film.
Pr Doped YBCO Films Produced by Pulsed Laser Deposition
Authors: Harrison B. Craig , Kell Joseph W. , Barnes Paul N. , Haugan Timothy J. , Varanasi Chakrapani V. , Rane Manisha V. , Ramos Frank , Maartense Iman
Published: April 2011

Pr doped YBa2Cu3O7-d targets with composition Y1-xPrxBa2Cu3O7-d where × = 0.0001, 0.001, 0.01, and 0.1 were prepared from oxide powders and were used to deposit thin films by pulsed laser deposition using conditions previously optimized for pure YBa2Cu3O7-d. The Pr dopant was found to be dispersed throughout the film by secondary ion mass spectrometry and found to have an increased density of nanoparticles on the surface. The pinning force of the doped samples was found to decrease with increasing concentration of Pr; however, at 0.01% concentration the doped film displayed a significant enhancement over pure YBa2Cu3O7-d for nearly the full range of 0 – 9 T.
Density Fluctuation in Coulombic Colloid Dispersion: Self-Assembly of Lipid A-Phosphates
Authors: Paradies Henrich H. , Faunce Chester A.
Published: April 2011

Dilute electrostatically–Vstabilized aqueous solutions of hexa-acylated (C14)lipid A-diphosphatefromEscherichia coliwere prepared with low polydispersities in shape, size and charge. A high degree of ordering was exhibited for volume fractions between Φ ≅ 1.5 × 10−4and 3.5 × 10−4. The structure factor S(Q) was strongly dependent on the particle number density, the nature of ions, e.g. Ca2+, Mg2+, K+, Na+and H+, the effective colloidal charge (Z*), and the Debye screening length,k. The magnitude and position of the S(Q) peaks vary not only with counterions, e.g. Ca2+or Mg2+, and concentration (nM to μM), but also with the order of their addition to thelipid A-dispersions. Different types of colloidal-crystal structures were obtained for Φ ≅ 3.5 × 10−4. The Ca2+and K+salts exhibited FCC type-lattices with a = 56.3 nm and 55.9 nm, whereas the Na+and Mg2+salts oflipid A-diphosphateformed BCC type-lattices with a = 41.5 nm and 45.5 nm, respectively.
Scaling Properties of two-dimensional Star-branched Polymers grown by Diffusion
Authors: Ramirez-Santiago Guillermo , Mendoza Carlos I.
Published: April 2011

We present an off-lattice numerical algorithm based upon pure diffusion to construct two-dimensional star-branched polymers with one, three, six and twelve branches. We built up structures with a total of up to 30,000 monomer units. For each one of them averages over one hundred independent configurations were taken. From a finite size analysis the scaling properties of the pair correlation function as well as the radius of gyration were obtained. Our findings indicate that the fractal dimension of the structures are: df=1.21 (0.03) for a linear polymer, df==1.21(0.02), for three branches, df==1.23 (0.02) for six branches and df=1.26 (0.03) for twelve branches.
Electric Field Guided Self-Assembly of Molecules
Authors: Lu Wei , Salac David
Published: April 2011

Adsorbate molecules usually carry electric dipole moments, and the magnitude can be engineered by adding polar groups. This paper investigates the dynamic domain pattern formation of multilayer dipolar molecules on a substrate under the guidance of external electric fields. The simulations reveal self-alignment, pattern conformation and the reduction of feature size in multilayer systems. A novel approach of transporting molecules on a substrate surface by reconfigurable molecular vehicles and embedded electrodes is proposed.
Switching of Water Flow Through Stimuli-responsive Hydrogels
Authors: Suzuki Atsushi , Kondo Go
Published: April 2011

The friction between the polymer network and the solvent water was measured by a newly designed simple apparatus where the hydrogel was mechanically constrained in a glass microcapillary. The water-flow through the hydrogel could be continuously controlled by more than ten times only by adjusting the temperature in the vicinity of the transition temperature (around the human body temperature). The concentration of polymer network and cross-linker as well as the inhomogeneity of polymer networks introduced at gelation was found to determine the overall flow velocity and the amount of change during the phase transition could be controlled by the temperature change. The principle to control the solvent flow will be discussed on the basis of the material parameters and the experimental conditions.
A Novel Associative Polymer Network based on Cyclodextrin Inclusion with Tunable Rheological Properties
Authors: Fu Lin , Guo Xuhong , Lincoln Stephen , Prud'homme Robert K.
Published: April 2011

A novel associative polymer network with tunable rheological properties is developed based on cyclodextrin-hydrophobe inclusion. The network is formed from mixtures of two polyacrylic acid (PAA) backbone polymers, one with pendant cyclodextrin groups and one with pendant hydrophobic alkyl groups. The lifetime of the cyclodextrin-hydrophobe inclusion can be well controlled by the length of alkyl chains inserted into the cyclodextrins; also, the binary nature of cyclodextrin-hydrophobe inclusion prevents hydrophobes from forming non-stoichiometric multiple associations. This system can serve as a model associative polymer network to test associative polymers theories. Dynamic rheological properties of this mixture solution can be tuned by adding free cyclodextrins or sodium dodecylsulfate (SDS) to displace polymer to polymer associations. Dynamic moduli change three orders of magnitude from a gel state to a sol state. This polyelectrolyte system is also pH sensitive, salt sensitive and temperature sensitive. The phase behavior of this mixture solution is experimentally studied by light scattering measurements and rheology. The thermodynamics of the cyclodextrin-hydrophobe interaction is independently studied using isothermal titration calorimetry and surface plasmon resonance study.
Chemo-electrical energy conversion of Adenosine triphosphate in a Biological Ion Transporter
Authors: Sundaresan Vishnu Baba , Sarles Stephen Andrew , Goode Brian J , Leo Donald J
Published: April 2011

Ion transport across cell membranes happens through protein channels and pumps expending concentration gradients, electrical gradients and energy from chemical reactions. Ion exchange in cell membranes is responsible for nutrient transport from production sites to where they are broken down to release energy. Sucrose transport is vital for growth in higher plants and recent research has led to the discovery of a class of sugar carriers called SUT4. The SUT4 transporter is a low affinity, high capacity proton-sucrose transporter that participates in long distance sucrose transport in higher plants. We demonstrated the possibility to use purified SUT4 transporter proteins — with the genetic code from Arabidopsis thaliana expressed on yeast cells — for fluid transport driven by pH gradient and from exergonic ATP hydrolysis reaction in the presence of ATP-ase enzyme. The SUT4 proteins were reconstituted on a planar bilayer lipid membrane formed from 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) phospholipids on a porous substrate. This article builds upon our previous work to harness energy from the ATP-ase reaction using SUT4 to produce a proton current through SUT4 and demonstrates the technical feasibility to generate electrical current in an external circuit. The results from our characterization experiments on a single cell demonstrate that the power source behaves like a constant current power source with an internal resistance of 10-22 kΩ and produces a peak power of 150 nW.
Nanocomposite with Very Large Electro-optic Effect and Widely Tunable Refractive Index
Authors: Chen Qin , Lin Minren , Lee Jonathan E , Zhang Qiming , Yin Shizhuo
Published: April 2011

Very large electro-optic effect has been observed in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) ( P(VDF-TrFE-CFE) ) terpolymer. By adding small amount of zinc sulfide (ZnS) nanoparticles, the refractive index of the nanocomposites can be tuned between about 1.4 and 1.5 while retaining large electro-optic effect and high transparency. Tunable long-period fiber gratings have been fabricated with the nanocomposite as the second cladding, and over 50nm of resonant wavelength shift has been achieved under a change of electric field of 30V/μm, which is much larger than other reported E-O tuning ranges. This corresponds to a pure refractive index change of the nanocomposite of Δn/n ∼ 0.4%.
A Study on Formation of Needle-like Polyanilines
Authors: Jung Woo-Hyuk , Kim Dong-Young , Lee Young-Moo , McCarthy Stephen P.
Published: April 2011

Needle-like polyanilines (PANi) were prepared at 15 °C by emulsion polymerization and their conductivities were obtained up to 3 S/cm according to the addition rate of ammonium peroxysulfate (APS) aqueous solutions with reaction conditions of 0.4 to 0.5 APS/aniline ratios and 0.4 to 0.5 M aniline concentrations. Needle-like complexes doped with p-toluenesulfonic acid (pTSA) were prepared with the oxidant solution added so slowly as to be for 3 to 3.6 hours. The high reaction temperatures ranging from 5 to 15 °C was the second condition to have needle-like anilinium complexes polymerized without their breaking during polymerization. A filler shape is one of the most important parameters influencing a percolation concentration of conductive fillers dispersed in a non-conductive matrix. Needle-like polyanilines could be potentially used as conductive fillers to show electromagnetic interference and radar absorption effects.
Resonant Sensors for Microfluidic Applications
Authors: Niebelschütz Florentina , Tonisch Katja , Cimalla Volker , Brückner Klemens , Stephan Ralf , Hein Matthias , Schober Andreas , Ambacher Oliver
Published: April 2011

In this work we present both resonators working at ambient conditions and their first application as a biological and physical sensor. Singly- and doubly-clamped resonators of different geometries were realized using active layers of silicon carbide and aluminum nitride. The resonators were excited by magneto-motive actuation. The quality factor reached 350 and 50000 in air and in vacuum (2-5 10−5 mbar), respectively, which is sufficient for sensing applications in air. The resonance shift caused by mass loadings in the range of picograms and by single biological cells was measured at ambient conditions. Initial non-resonant measurements in liquids such as propanol were performed to investigate the possibility of viscosity measurements in small volumes such as microfluidic channels and droplets.
Gas Sensor Based on the Network of SnO2 Semiconducting Nanowires
Authors: Choi Young-Jin , Hwang In-Sung , Choi Kyoung-Jin , Park Jae-Hwan , Park Jae-Gwan
Published: April 2011

A simple and efficient way of preparing highly sensitive SnO2 nanowire-based gas sensors without an arduous lithography process was studied. The network of SnO2 nanowires could be suspended upon the Si substrate by separating the Au catalyst layer from the substrate. As the electric current is transported along the networks of the nanowires, not along the bottom layer on the substrate, the sensitivity to gases was maximized in the suspended and networked structures. The sensitivities were 18 and 180 when the NO2 concentrations were 0.5 and 5 ppm. The response time was typically 20-50 s.
Fabrication of Nanostructured ZnO UV Sensor
Authors: Hullavarad Shiva S. , Hullavarad N. V. , Mooers M. , Karulkar P. C.
Published: April 2011

In this paper we describe the fabrication of nanostructure based ZnO ultra violet sensor by a simple route without involving the clean room processing of inter digitized electrodes. The ZnO nanostructures consist of micro spheres of dimension 600 nm- 2 microns embedded in the network of nanowires of dimension 40 nm. The optical properties are studied by Photoluminescence spectroscopy that revealed the exciton band gap of 3.2 eV at 383 nm. The ultra violet sensors exhibit 2 orders of UV to visible rejection ratio. The photo response of Ultra violet sensors as a function of electrode spacing will be discussed.
Rapid Label-free Protein Detection Arrays on Coated Silicon Wafers
Authors: Striemer Christopher C. , Mace Charles R. , Miller Benjamin L.
Published: April 2011

We are developing label-free Arrayed Imaging Reflectometry (AIR) for rapid and multiplexed protein detection. AIR is based on the high dynamic range in reflected optical intensity near a point of zero reflectance on an antireflection coated substrate. The reflectance is therefore highly sensitive to changes in film thickness, allowing direct detection of molecular binding when appropriate probe molecules are immobilized on the surface. The simplest implementation of AIR uses a 633 nm HeNe laser and a silicon wafer substrate coated with ∼1400 Å of SiO2. This system has a reflectance zero for s-polarized HeNe light incident at ∼70°. This interference film is then functionalized with probe molecules designed to bind to a specific target, and this binding can be detected with high sensitivity in the reflectance signal. By expanding the laser beam and collecting the reflected signal with a CCD camera, large arrays of detection spots can be imaged simultaneously. Spot intensity increases relative to the amount of target binding and the target solution concentration can then be calculated. We have demonstrated the detection of the Enteropathogenic E Coli membrane protein Intimin at levels below 10 pM using receptor molecule Tir as a probe, and are currently evaluating various clinical targets using more common antibody probes.
AAO Nanowells: Synthesis, in-situ Growth Study, and Applications in Ultra-sensitive Chemical Detection
Authors: Wang H. Hau , Son Kyung-In , Lee Byeongdu , Lu Jianjiang , Han Catherine
Published: April 2011

Anodized aluminum oxide (AAO) membranes consist of locally highly ordered nanopores. The pore diameter (20-200 nm) and pore-to-pore distance are controlled through the anodizing voltage and the choice of etching solution. High aspect ratio over 1,000 can easily be achieved which makes AAO membranes the ideal templates for making nanowires and nanotubes. In this work, the early stage of nanopore formation was studied in-situ with the use of small angle x-ray scattering (SAXS) and glazing incidence GISAXS techniques. The nanopores were found to grow as a function of the square root of growth time. The resulting short nanopores or nanowells with length below 200 nm were further characterized with use of SEM and AFM. These AAO nanowells showed interference color. Their reflectance UV-Vis spectra indicated strong angular dependence and can be understood with a simple single layer (nanoporous alumina over aluminum) model. These spectra are influenced by the nanowells thickness and diameter. Therefore, large array of interferometric AAO nanowells sensors are possible. When these nanowells are coated with Ag or Au thin films, in addition to enhanced interference color, highly sensitive surface enhanced Raman scattering (SERS) effect has been observed. These results will be presented.
Fabrication of Nanostructured Thin Films Using Porous Alumina Templates
Authors: Yin Aijun , Kim Jin Ho , Xu Jimmy
Published: April 2011

We demonstrate a method for fabricating a variety of nanostructured metallic thin films by using one simple approach based on the use of anodic aluminum oxide (AAO) membrane as masking template. Highly-ordered large-area metallic nanopore- or nanotip-arrays (e.g., Ni, Ag, Au), with various sizes and shapes, were deposited onto AAO membranes through e-beam evaporation. Free standing nano-patterned metallic films were obtained after chemically removing the template and characterized using scanning electron microscopy and electrochemical methods. The nanostructured films will find use in a number of applications, such as plasmonics, electrochemical and biomedical analysis, and catalysis.
Physically Self-assembled Au Nanorod Arrays for SERS
Authors: Suzuki Motofumi , Nakajima Kaoru , Kimura Kenji , Fukuoka Takao , Mori Yasushige
Published: April 2011

We have demonstrated surface-enhanced Raman spectroscopy on arrays of Au nanorods aligned in line by a dynamic oblique deposition technique. For the light polarized along the major axis of the nanorods, the plasma resonance of the Au nanorods has been tuned to a wavelength suitable for Raman spectroscopy. The Raman scattering on the discrete nanorods is enhanced significantly compared with that on semi continuous Au films. Since the preparation process is physically bottom-up, it is robust in its selection of the materials and is useful in providing the SERS sensors at low cost.
Plasma Surface Functionalization of Poly[bis(2,2,2-trifluoroethoxy)phosphazene]
Authors: Steely Lee B. , Allcock Harry R. , Kim Seong H. , Kim Jeong H. , Kang Bang-Kwon
Published: April 2011

Polyphosphazenes have a highly flexible backbone comprised of nitrogen and phosphorus atoms with two organic groups on each phosphorus. Materials in this class are inherently thermo-oxidatively stable, soluble, and chemically resistant especially when a variety of fluorinated organic groups are attached to the backbone. Several solution based side group exchange reactions have been examined previously that have profound effects on the surface topology, but may present problems for large scale production. We have utilized a high-throughput process for surface functionalization of polyphosphazenes to yield films with excellent chemical properties that can be tuned by surface treatment with plasma gases.

Films of the poly[bis(2,2,2-trifluoroethoxy)phosphazene] were surface functionalized with plasmas of methane, oxygen, or nitrogen gases. An environmental plasma head was used to treat the spuncast films with free radicals in the treatment gases. These surface treatments were characterized by XPS and water contact angle methods to determine the modified surface structure of the films and the effect on surface properties. More than 90° changes in water contact angle are possible, depending on the plasma used and the density of surface functionalization. Tuning of the water contact angle was also possible from the native 101° static contact angle of poly[bis(2,2,2-trifluoroethoxy)phosphazene] to approximately 70°, 40°, or 4° with appropriate treatment using methane, nitrogen, or oxygen plasmas. Using XPS surface surveys we found that the fluorine concentration on the surface was higher than in the bulk material. Significant changes in the carbon, oxygen, and nitrogen 1s binding energies of the samples were also detected that varied with plasma treatment.

This process allows polyphosphazene polymers or copolymers to be surface functionalized as an alternative to other processes where delamination or differences in thermal or chemical properties would preclude a traditional two polymer composite approach. Printing of controlled patterns with a cover mask are also possible to create a surface with several distinct regions of hydrophobicity or hydrophilicity or of functional groups all of which may be applicable in microfluidics, printing, adhesion, or sensor arrays.
Active Signal Processing: A Counter-intuitive Approach to Enhancing Signal-to-Noise Ratio via Noise Injection
Authors: George Thomas , Gulati Sandeep , Menahem Shahar Ben , Breaux James K , Boysen Cecilie , Daggumati Vijay , Quon Ronald
Published: April 2011

Since its origin in the early 1980s, the noise-injection based stochastic resonance technique has spearheaded a novel counter-intuitive approach toward improving sensor performance. Within this approach, named Active Signal Processing, instead of removing system noise by filtering (Passive Signal Processing), it is possible to improve signal-to-noise ratio (SNR) by injecting noise into the measurement. ViaLogy LLC. has pioneered the development and demonstration of Quantum Resonance Interferometry (QRI), a quantum stochastic resonance (QSR)-based technique for improving SNR. The core of QRI processing involves the QSR-based generation of a Quantum Expressor Function (QEF), which characterizes the system of interest by encoding within it the noise environment, minimum level of detection, and the precision of measurement. Using digital post-processing of sensor information, QRI can determine the presence of a signal by the destruction of the resonance condition responsible for generating the system QEF. For applications aimed at detecting the presence of a weak signal, the strength of the signal is proportional to the number of iterations of the algorithm required for destruction of the resonance; the fewer the iterations, the stronger the signal. The application of QRI for detecting the presence of weakly expressing genes in fluorescent DNA microarrays will be described.
NanoParticle Tracking Analysis; The Halo System
Authors: Malloy Andrew , Hole Patrick , Carr Bob
Published: April 2011

A new technique for nanoparticle sizing that allows visualisation of nanoscale particles in liquids on an individual basis is described. The technology comprises a metallised optical element illuminated by laser beam at the surface of which nanoscale particles in suspension can be directly visualised, sized and counted in real time using only a conventional optical microscope fitted with a low cost camera and a dedicated analytical software package.
Polyethylene Glycol Deposition Techniques for Antifouling Surfaces: Using Antistiction to Conserve Bioparticles for Recovery and Analysis
Authors: Chang Norine E. , Lean Meng H. , Limb Scott J.
Published: April 2011

For bioparticle analysis within microfluidic devices, there is a risk of analytes adhering to surfaces, thereby compromising particle manipulation and recovery. To address this we have implemented polyethylene glycol (PEG)-type coatings by self-assembled monolayer (SAM) and plasma-polymerizing deposition techniques. Silane chemistry is used to deposit SAM films directly onto silicon dioxide surfaces, and in a special case for which a composite of metallic arrays and SiON within our MEMS device must be coated, an ultrathin layer of sputtered Si is added before the SAM protocol. We have also deposited PEG-like tetraglyme by plasma-polymerization onto substrates using an onsite-built reactor to provide antistiction treatment to all surfaces, including those that do not have chemical compatibility for the SAM technique. Three tests demonstrate the effectiveness of our surface treatments: static exposure to microbial suspensions, bioparticle transport across MEMS traveling-wave (TW) arrays, and bioparticle recovery from a circulating flow device. Our static microbial assays show significant reduction in B. thuringiensis adhesion to both the SAM and plasma-polymerized coatings and reduction in B. globigii adhesion to the plasma-polymerized coating. Our TW arrays, when coated with either the SAM or plasma-polymerized PEG film, are effective at reducing adhesion to polystyrene beads as well as both Bacillus species. Lastly, our bioparticle recovery, as gauged by spectrophotometry, improves by as much as one order of magnitude when we coat flow chambers with our plasma-polymerized film.
Spinodal Decomposition and Super-Paramagnetism in Dilute Magnetic Nitride Semiconductors
Authors: Sato Kazunori , Fukushima Tetsuya , Katayama-Yoshida Hiroshi
Published: April 2011

We discuss origin of ferromagnetism in dilute magnetic semiconductors (DMS) and propose accurate calculation method for Curie temperature from first-principles. For more realistic materials design, we simulate inhomogeneous impurity distribution due to the spinodal decomposition in DMS from first-principles. Combining these techniques, we discuss super-paramagnetism and blocking phenomena in DMS and propose fabrication method of DMS with high blocking temperature.
Gadolinium and Oxygen co-doping of Gallium Nitride: an LSDA + U study
Authors: Lambrecht Walter R. L. , Larson Paul
Published: April 2011

Results of first-principles supercell calculations for Gd impurities, with and without O-impurities in the same cell are presented. The possibility of colossal magnetic moments, as reported by Dhar et al., [Phys. Rev. Lett. 94, 037205 (2005)] is discussed in view of the results. Particular attention is paid to the size of the conduction band spin splitting, induced by Gd. It is argued that O plays a more active role than merely providing the electrons leading to the magnetic moment. Estimates are made of the splitting of the conduction band required to explain the occurrence of colossal magnetic moments.
Fabrication of high-performance photodetector based on AlGaN/GaN hetero-field-effect transistors with p-GaN gate
Authors: Miura Shuichi , Fujii Takahiro , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: April 2011

An AlGaN/GaN photo-hetero-field-effect transistor (photo-HFET) with a p-type GaN gate was fabricated and its properties were compared with those of a HFET without a p-type GaN layer. The photo-HFET with a p-GaN gate exhibited a high signal-to-noise ratio of five orders of magnitude and a dark current density of 10 nA/mm at a drain-source bias of 5 V. In contrast, when the photo-HFET was irradiated with 365 nm (490 μW/cm2) UV light, a photocurrent of over 1 mA/mm was achieved. The responsivity of the device was over 1 × 105 A/W.
Fabrication and Characterization of 2-inch diameter AlN Single-Crystal Wafers cut From Bulk Crystals
Authors: Bondokov Robert T. , Morgan Kenneth E. , Slack Glen A. , Schowalter Leo J.
Published: April 2011

Aluminum nitride (AlN) boules larger than 2 inches in diameter were grown by the sublimation-recondensation technique. X-ray Laue diffraction was used to characterize the crystallinity and orientation of the boules, and 2” dia. substrates were sliced with typical thickness of ∼500 μm. The wafers were then polished in order to meet the common standards for wafer thickness and flatness. The Al-terminated surface was finished with a proprietary chemical-mechanical process and showed RMS roughness of 0.5 nm or less as measured by atomic force microscopy (5×5 μm area). Currently, the substrates have some polycrystalline regions that are highly textured but about 85% of the total area is monocrystalline. The dislocation density in the crystalline regions of the substrate was measured by preferential chemical etching and then determining the resulting etch pit density (EPD). The etching technique involves potassium hydroxide and has been qualified through correlation with x-ray topography measurements of the dislocations. Measured EPD varied from 250 cm−2to 3×104cm−2. Other structural defects such as low angle grain boundaries, prismatic slip bands, inversion domains, have also been observed. The rare appearance of these defects will be discussed even though their role in the epitaxial growth of GaN and AlGaN is yet to be clarified.