bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring of Traumatically Injured Organotypic Hippocampal Cultures with Stretchable Microelectrode Arrays
Authors: Yu Zhe , Tsay Candice , Lacour Stéphanie P. , Wagner Sigurd , Morrison Barclay
Published: April 2011

Traumatic brain injury (TBI) can be caused by motor vehicle accidents, falls and firearms. Approximately 2% of the US population lives with disabilities cause by TBI. To discover mechanisms of functional deficits underlying TBI, as well as to develop strategies to restore lost function with neural interfaces, we developed a stretchable microelectrode array (SMEA), which can be used for continuous recording of neuronal function, pre-, during, and post-stretch injury. The SMEAs were fabricated on elastomeric substrates, consisting of stretchable 100μm wide, 25nm thick gold electrodes patterned on a polydimethylsiloxane (PDMS) substrate, and encapsulated with a 10-20μm thick, photo-patternable silicone (WL-5150, Dow Corning) insulation layer. Finally, the SMEA was packaged between two printed circuit boards and mounted in a commercial Multi Channel Systems amplifier. Combining with our TBI model, which can generate precise and reproducible injury of hippocampal cultures, SMEAs were able to monitor the extracellular field potentials of neuronal populations within the cultures grown on SMEAs and injured by bi-axialy stretching the stretchable membranes. Previous biocompatibility tests showed no overt necrosis or cell death caused by the SMEAs after 2 weeks in culture [2]. The electrical performance of the SMEAs was tested in electrophysiological saline solution before, during and after biaxial stretching. The initial electrode impedance at 1kHz was ∼2kΩ. The SMEA was stretched to 8.5% biaxial strain. The microelectrode impedance increased with the strain to reach 800kΩ at 8.5% strain. Upon relaxation, the impedance recovered to 10kΩ. The working noise level of the sMEA remained below 20 ΩVpp during the whole process. New methodologies for improving the design of microelectrode arrays structure, the choice of materials and the new technology of fabrication were tested on gold microelectrode arrays supported on glass. By using the prototype arrays, population spikes were able to be recorded from organotypic hippocampal slice cultures of brain tissue. Our results demonstrate that the prototype arrays have good electrical performance compatible with existing multielectrode array systems. Moreover, the results indicate the ability of the prototype arrays to record neuronal activity from hippocampal slices. This novel technology of SMEAs will enable new studies to understand injury mechanisms leading to post-traumatic neuronal dysfunction.
Precision Teng-Man Electro-Optic Measurements Using Highly Near-Infrared Transparent Electrodes
Authors: Wang Lian , Yang Yu , Liu Zhifu , Marks Tobin J. , Ho Seng-Tiong
Published: April 2011

A series of highly near-infrared (NIR) transparent In2O3 thin films has been grown by ion-assisted deposition (IAD) at room temperature, and their optical and electrical properties characterized. The NIR transparency and the plasma edge can be engineered through control of the film deposition conditions. The as-deposited In2O3 thin films were employed as transparent electrodes for direct electro-optic (EO) characterization measurements via the Teng-Man technique. Using LiNbO3 as the standard, the relationship between the degree of electrode NIR transparency and Teng-Man EO measurement accuracy was evaluated. It is found that In2O3 electrodes can be tailored to be highly NIR transparent, thus providing more accurate Teng-Man EO coefficient quantification than ITO (tin-doped indium oxide). In addition, the EO coefficients of stilbazolium-based self-assembled superlattice (SAS) thin films were directly determined for the first time by the Teng-Man technique using an optimized In2O3 electrode. EO coefficients r33 of 42.2, 13.1, and 6.4 pm/V are obtained at 633, 1064, and 1310 nm, respectively.
Structural and Microwave Characterization of Magnetron Sputtered Ba0.5Sr0.5TiO3 Films on c-plane Sapphire Substrates
Authors: Fardin Ernest Anthony , Holland A. S. , Ghorbani K. , Usher B. F.
Published: April 2011

Many studies of Barium Strontium Titanate (BST) thin films for RF / microwave applications have employed MgO, LaAlO3 or Pt/Si as the substrate material for BST deposition. However, there have been relatively few reports of BST films grown on sapphire, despite the excellent microwave properties of this material. In this investigation, BST thin films were deposited by RF magnetron sputtering on (001) single crystal c-plane sapphire substrates. Interdigitated capacitors (IDCs) patterned on the film surface were used to measure the dielectric tunability and loss tangent at microwave frequencies. Thick Au conductors were electroplated to minimize conductor losses. Post deposition annealing in air was found to significantly improve the tunability of the sputtered films.
Enhanced contrast ratio of an electrochromic window (ECW) based on a V2O5-TiO2 composite thin film as a counter electrode
Authors: Kim Sooyeun , Xu Chunye , Taya Minoru
Published: April 2011

An Electrochromic window (ECW) is a strong candidate for an optical shutter. An ECW is composed of the conductive polymer as a working electrode and V2O5 as a counter electrode. The ECW technology switches between colored and bleached stages. In this paper the modification of a V2O5 thin film as a counter electrode is studied to increase contrast ratio of ECWs by adding TiO2 into V2O5. The dependence of the intercalation properties and transmissivity of V2O5-TiO2 composite films on various chemical compositions, a preparation and characterization of the films for use as a transparent ion storage layer in organic ECWs are focused on in this paper. A V2O5-TiO2 composite film was synthesized with sol-gel electrophoresis deposition method. Indium Tin Oxide (ITO) coated glass was used as an electrically conductive and transparent substrate. A V2O5-TiO2 composite film with V/Ti ratio of 70/30 in the reduced state showed 6 to 13% improvement of transmissivity between 380 nm and 800 nm wavelengths as compared to a V2O5 thin film in the same state. Li+ intercalation rate was also observed to be higher. The composite film exhibited twice of capacitance than that of the V2O5 film. An ECW with the composite film exhibited 6% higher contrast ratio than that with the V2O5 film. The contrast ratio of the ECW, measured as Δ%T, was equal to 56%, and ranged from 2% to 58% between the colored and bleached state measured at 580 nm wavelength. The color change response speed was also faster, i.e., only two seconds between fully colored and bleached stages.

Key words: electrochromic window (ECW), V2O5-TiO2 composite film, contrast ratio, transmissivity, Li+ intercalation rate
High Flux Polyamide Composite Hollow Fiber Membranes for Reverse Osmosis Applications
Authors: Norris Ian D. , Morrison Malcolm C. , Mattes Benjamin R.
Published: April 2011

High flux composite hollow fiber membranes for brackish water desalination based on the interfacial polymerization of a cross-linked polyamide salt rejecting layer onto a semi-permeable hollow fiber support have been developed. These hollow fiber membranes exploit the advantages of using a thin-film composite reverse osmosis membrane (higher flux and salt rejection) with the higher surface area/volume ratio of hollow fiber membrane elements. The composite hollow fiber membranes were prepared by coating a polysulfone hollow fiber with a polyamide salt rejecting layer based on the interfacial polymerization reaction between m-phenylenediamine and trimesoyl chloride/isophthaloyl dichloride. The RO figures-of-merit of these composite polyamide hollow fiber membranes were evaluated for the desalination of a synthetic brackish water feed (2,000 ppm NaCl) at 225 psi over a 60 hour period. After an initial break-in period in which the flux declined 30% due to membrane compaction, the stabilized RO figures-of-merit for these hollow fiber membranes were a water flux of 280 L/m2·day and a salt rejection of 99.1%. Based on the water flux and packing density of the membrane, it is estimated that the stable production of potable water of a hollow fiber membrane element containing these composite membranes will be between 20 and 30% greater than that of a similarly sized spiral wound brackish water membrane element.
Does Exceptional Viscous Drag Impede Flow Through a Nano-Sieve's Pores?
Authors: Feibelman Peter J. , Houston J. E.
Published: April 2011

To address the concern that a material functionalized to reject dissolved ions may give rise to a highly viscous aqueous interphase within nanometers of its surface, we conducted and interpreted Interfacial Force Microscope measurements of the dissipative forces that resist motion of a tip parallel to a sample, in water. The results are consistent with earlier measurements where the tip approached the sample. They confirm that near hydrophilically functionalized surfaces, interphase viscosities more than a million times that of bulk water can be expected.
Including Nanoscale Investigations in Undergraduate Physics Laboratories at all Levels of the Curriculum
Authors: Vandervoort Kurt , Hyder Asif , Barker Stephanie , Torrico Raul
Published: April 2011

A series of laboratory modules were developed to introduce atomic force microscope (AFM) applications into undergraduate physics courses. The goal is to elucidate fundamental physics concepts at the nanoscale that will complement existing investigations at the macroscale, and to expose students to advanced instrumentation at an early level. The experiments allow students to experience the full range of scanning probe modes available, which include contact, intermittent contact, lateral force, and magnetic force microscopy as well as force distance spectroscopy. The course levels span the range from freshman introductory to advanced senior level and allow students to experience AFM applications at successive levels of complexity.
Real Time Nanostructure Imaging for Teaching Nanoscience and Nanotechnology
Authors: Chizmeshya A. V. G. , Drucker J. , Sharma R. , Carpenter R. W.
Published: April 2011

Our experiences in research on nanoscience and technology using various microscopies to observe materials synthesis reactions and to measure local (∼ 0.1-100 nm scale) structure and composition variations in solids provide some very useful examples to introduce students to important concepts of the field. The fundamental concept to illustrate is the nanometer length scale, of course, but other concepts such as mass and energy flows at the nanometer level and their effects on materials properties are at least as important, but more difficult to bring to students in a challenging but understandable way. We are using dynamicin situor animated microscopy experiments in several material systems to teach these concepts. These experimental research results provide a useful basis for student computer modeling experiments, to give them direct participation in nanoscale materials research at an appropriate level. We are also exploring student group participation in live (interactive) electron microscopy experience via remote access into a suitably equipped computer visualization classroom.
Size dependence in one-dimensional nano-materials and one-dimensional heterojunctions
Authors: Zhu Jing , Luo Jun , Chen Changqiang , Shi Yu , Liu Xiaohua , Zhang Jiong , Peng Kuiqing , Huang Zhipeng
Published: April 2011

One-dimensional (1D) nano-materials have attracted a plenty of attention due to their novel structures and properties. Our group has carried out researches on synthesis, structure and property of 1D nano-materials, which are introduced in this paper. First, size effects on the crystal structure of Ag nanowires and on Young's modulus in [0001] oriented ZnO nanowires, respectively, have been revealed and modeled. The former is concerning the systemic energy of an individual Ag nanowire. The latter is caused by the surface stiffening effect arising from surface relaxation induced bond length contractions in the ZnO nanowires. Second, structures of 1D helical nano-materials including SWCNT (single-walled carbon nanotube), B-DNA and MWCNT (mutli-walled carbon nanotube) have been studied. It is shown that there is strong orientation dependence of diffraction intensities from SWCNT and B-DNA, which can even result in certain layer lines missing in their diffraction patterns. Also, it is demonstrated that high-resolution transmission electron microscope (TEM) images of sidewall regions of MWCNTs are not structural ones and from the interference of the {0002} and the {1011} diffraction waves. Third, arrays of four types of 1D heterojunctions have been synthesized. Among these 1D heterojunctions, the interfacial structures of the Ni/MWCNT/a-CNT(amorphous carbon nanotube) heterojunctions show that multiple outer walls in the MWCNTs can simultaneously participate in electrical transport. The electrical properties of the Ni/MWCNT/a-CNT and the Ag/a-CNT heterojunctions have been measured. As a result, it is found that the contacts between the Ag nanowires and the a-CNTs are ohmic ones with universal significance, and that each Ni/MWCNT/ a-CNT contains two diodes connected in series face-to-face. Moreover, most of the diodes have the most nearly ideal characteristics of Schottky contacts, indicated by quantitative analysis with the thermionic emission theory. Last, our group has developed a novel technique for rapidly producing large-area highly-oriented Si nanowire arrays on Si wafers by scratching the Si surface with metal nanoparticles near room temperature in HF solution. By this method, Si nanowires with desirable axial crystallographic directions, desirable doping characteristics and remarkable antireflection property can be readily obtained. The Si nanowire arrays have the potential applicability as an antireflective layer for photovoltaic devices and optical detectors. Furthermore, a combination of this method and the nanosphere lithography has been developed to fabricate large-scale Si and Si1−xGex quantum dot arrays with controllable height, diameter and center-to-center distance.
Low-Temperature Hetero-Epitaxial Growth of Ge on Si by High Density Plasma Chemical Vapor Deposition
Authors: Carroll Malcolm , Sheng Josephine , Verley Jason C.
Published: April 2011

Demand for integration of optoelectronic functionality (e.g., optical interconnects) with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation of low temperature (∼ 450°C) germanium deposition processes that may be integrated in to the back-end CMOS process flow. A common challenge to improving the germanium quality is the thermal budget of the in-situ bake, which is used to reduce defect forming oxygen and carbon surface residues. Typical cleaning temperatures to remove significant concentrations of oxygen and carbon have been reported to be approximately 750°C for thermal hydrogen bakes in standard chemical vapor deposition chambers. Germanium device performance using lower peak in-situ cleans (i.e., ∼450°C) has been hampered by additional crystal defectivity, although epitaxy is possible with out complete removal of oxygen and carbon at lower temperatures.

Plasma enhanced chemical vapor deposition (PECVD) is used to reduce the processing temperature. Hydrogen plasma assisted in-situ surface preparation of epitaxy has been shown to reduce both carbon and oxygen concentrations and enable epitaxial growth at temperatures as low as ∼150°C. The hydrogen is believed to help produce volatile Si-O and H2O species in the removal of oxygen, although typically this is not reported to occur rapidly enough to completely clear the surface of all oxygen until ∼550°C. In this paper, we describe the use of an in-situ argon/germane high density plasma to help initiate germanium epitaxy on silicon using a peak temperature of approximately 460°C. Germanium is believed to readily break Si-O bonds to form more volatile Ge-O, therefore, argon/germane plasmas offer the potential to reduce the necessary in-situ clean temperature while obtaining similar results as hydrogen in-situ cleans. To the authors knowledge this report is also the first demonstration of germanium epitaxy on silicon using this commercially available high density plasma chamber configuration instead of, for example, remote or electron cyclotron resonance configurations.
The Medium-Depending Fluorescence of Quadrupolar Donor-Acceptor-Donor Substituted Distyrylbenzenes with High Two-Photon Absorption Cross-Sections
Authors: Detert Heiner , Schmitt Volker , Glang Stefan
Published: April 2011

1,4-Distyrylbenzenes with terminal dialkylamino groups and a central 2,5-disubstitution with electron-accepting groups were prepared via twofold Horner-olefination. These chromophores with a quadrupolar donor-acceptor-donor substitution and C2-symmetry absorb in the violet to green region of the visible spectrum exhibit large two-photon-absorption cross-sections when irrdiated in the NIR. Whereas a variation of the solvent polarity only slightly alters the absorption spectra, the fluorescence appears to be highly responsive. Besides a positive solvatochromism, the emission is very sensitive towards protonation. Quenching or appearance of new emitting species depends on the substitution pattern and is controlled by the concentration of the acid.
Bi-stable State for WORM Application Based on Carbazole-containing Polymer
Authors: Teo Eric Yeow Howee , Ling Qidan , Song Yan , Tan Yoke Ping , Wang Wen , Kang En-Tang , Chan Daniel Siu Hung , Zhu Chunxiang
Published: April 2011

Recently, several studies have been done by various groups to understand the memory effects behind organic materials, which include understanding in terms of conformation changes, conjugation modification and oxidation-reduction process. In this paper, a WORM (write-once read-many times) memory device using a new polymer material 2-(9H-carbazol-9-yl)ethyl methacrylate (PCz) containing carbazole donor group has been demonstrated. The device uses a MIM (metal-insulator-metal) structure with ITO coated glass as bottom electrode, the synthesized polymer material PCz as the active layer and Al as the top electrode. The toluene solution of PCz was spin-coated on the ITO, followed by solvent removal in a vacuum chamber. Finally, Al was thermally evaporated through shadow mask onto the PCz film.

The memory effect of PCz was observed in the I-V characteristic of the MIM structure. The as-fabricated device is found to be in its OFF state, and can be programmed to ON state which is not reversible. The WORM device exhibits a high ON/OFF current ratio of up to 106, and shows a good retention time for both the ON and OFF states which can be sustained within a 24 h timeframe, and extrapolated to sustain for another 10 years. The effect of continuous read pulse on the ON and OFF states was evaluated and no resistance degradation is observed for read cycles up to 107 times. By comparing the electrical characteristics of PCz and PVK as well as their optimized geometry simulation corresponding to their minimized energy states, the memory effect or bi-stable states of PCz can be attributed to the long linker between the carbazole groups and backbone present in PCz which play a part in the conduction mechanism.
Ab inito Calculation of Electron Transport Through Single Molecules by the RTM/NEGF Method
Authors: Hirose Kenji , Kobayashi Nobuhiko
Published: April 2011

Using the recursion-transfer-matrix (RTM) method, which is a powerful method to obtain accurate scattering waves, combined with non-equilibrium Green's function (NEGF) method, we study the transport properties through single molecules sandwiched between electrodes with finite bias voltages. Especially, we investigate the effects of atomic-scale contacts on the I-V characteristics. We find strong nonlinear behaviors appear in the I-V characteristics when the atomic-scale contact at one electrode is not formed well.
Single Crystal InSb Nanowires: Synthesis, Characterization, Properties and Applications
Authors: Ye Qi Laura , Yamada Toshishige , Liu Hongbing , Scheffler Raymond , Mingo Natalio , Leverenz Ryan
Published: April 2011

We report the first large-scale synthesis of single crystal InSb nanowires using vapor-liquid-solid (VLS) transport process. Narrow growth window for achieving single crystal InSb nanowires has been discovered. Our batch produced InSb nanowires are 50-180 nm in diameter and 10-30 μ in length. Materials composition analysis by Energy-Dispersive X-ray Spectroscopy (EDAX) reveals that the as-grown InSb nanowires are pure single crystals of InSb. Structural analysis by High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) reveals that InSb nanowires have body-centered-cubic (BCC) crystal structure with cubic unit cell length of 10.15 Å. The nanowire growth direction is found to be [001], 45 degrees toward the most dense lattice planes in BCC structure.
Growth of GeO2 Nanowires by Thermal Annealing
Authors: Wu Chun-I , Hogan T. P.
Published: April 2011

Germanium dioxide nanowires have gained considerable interest lately [1, 2], in part this is due to the bandgap of 2.44 eV, and high index of refraction, n = 1.63 [3]. In this paper we report a simple fabrication technique for making large quantities of GeO2 wires with diameters ranging from 40 nm to >500 nm on different substrates. The nanowires show strong preferential growth at gold catalyst locations on the silicon substrate. The nanowires were grown on silicon, tungsten, quartz, and nickel substrates at locations where a ∼10 nm film of Au was deposited. Growth and diameter of the wires are strongly dependent on the background gas (room air) and the length of time exposed to air at the growth temperature. Presented here are the growth conditions, and images of the resulting wires fabricated. The products are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) as well as X-Ray diffraction (XRD). The observations show the products are crystalline GeO2 nanowires.
Large Nonlinear Kerr Angle in non-Centrosymmetric Fe/AlGaAs (001) Heterostructure
Authors: Zhao Haibin , Talbayev Diyar , Luepke Gunter , Hanbicki Aubrey , Li Connie , Jonker Berend
Published: April 2011

A large nonlinear magneto-optical effect is observed in a non-centrosymmetric Fe/AlGaAs (001) heterostructure. This effect is a direct consequence of interference between second-harmonic optical waves of magnetic and crystallographic origin, generated at ferromagnetic Fe interface and bulk AlGaAs, respectively. The longitudinal nonlinear Kerr rotation is measured to be 1.6° along the [1-10] hard axis, about two orders of magnitude stronger than the linear equivalent. The rotational second-harmonic signal shows large magnetic contrast along all the in-plane directions, demonstrating a high sensitivity to the magnetization of an anisotropic interface in the longitudinal geometry.
Onset of Exchange Anisotropy in Epitaxial fct-Cobalt(001)/fct-Manganese(001) Bilayers
Authors: Kohlhepp Jürgen T. , Wieldraaijer Harm , de Jonge Wim J. M.
Published: April 2011

Manganese (Mn) grows in a meta-stable expanded (c/a > 1) face-centered-tetragonal (fct) phase on thin fct-Co(001) template films. For small Mn thicknesses a close to a layer-by-layer growth is observed. Antiferromagnetism (AFM) of fct-Mn is evidenced by the observation of shifted magnetization loops antiparallel to the cooling field direction (negative bias) and enhanced coercive fields for Co/Mn bilayers. At low temperatures magnetic Co/Mn interface exchange interactions are detected for nominal Mn thicknesses as low as 1.3 monolayer (ML), indicating the onset of AFM in 2 ML thick Mn islands. However, between 2 ML and 5 ML Mn a positive bias of the magnetization loops is observed in a certain temperature range below the blocking temperature (TB) of the films. This peculiar behavior is explained by the dependence of TB on both the local Mn ML thickness and the Mn island size, leading to a unidirectional coercivity enhancement in a temperature range where both blocked and unblocked regions are coexisting in the Mn layers.
Magnetic Rare Earth (Gd) Implanted Tetrahedral Amorphous Carbon (ta-C)
Authors: Zeng Li , Helgren Erik , Zutz Hayo , Ronning Carsten , Hellman Frances
Published: April 2011

Tetrahedrally bonded amorphous carbon (ta-C) thin films were prepared by mass selected ion beam deposition (MSIBD) using 100 eV carbon ions at room temperature. Gadolinium, a magnetic rare earth element, was implanted as a dopant into ta-C with two different fluences. The doping level of the ta-C:Gdx layers was in maximum 4 or 7 at.%, respectively. The Gd is believed to be electrically activated in as-implanted films, although contributions from the sp2 sites cannot be ruled out. A transition temperature (T') was found, below which there is a large negative magnetoresistance (MR) with a strong temperature dependence. Thermal annealing greatly increases the sample conductivity due to the increase of sp2 sites. However, the MR persists at least up to an annealing temperature of 500°C. Magnetically, the Gd dopants behave like non-interacting local moments. Similarities and differences in physical properties between the ta-C:Gdx films and other Gd doped amorphous semiconductors are compared.
A Novel Simple Route to Synthesize Aqueous Niobium and Tantalum Precursors for Ferroelectric and Photocatalytic Applications
Authors: Li Ai-Dong , Cheng Jin-Bo , Tang Rong-Lu , Shao Qi-Yue , Tang Yue-feng , Wu Di , Ming Nai-Ben
Published: April 2011

A simple novel route to synthesize aqueous tantalum and niobium precursors has been developed using cheap and stable Nb2O5 or Ta2O5 as starting source, based on basic flux technique. Various analytical techniques have been employed to characterize the purity, and thermal decomposition features of the precursors. Using home-made Ta and Nb precursors, several photocatalysts and ferroelectric powders such as LiNbO3, LiTaO3, Sr0.75Ba0.25Nb2O6, and SrBi2Ta2O9 have been prepared at lower processing temperature by a polymerizable complex route successfully.
Wet-Chemical Synthesis of ZnTe Quantum Dots
Authors: Zhang Jun , Sun Zhaoyong , Fang Jiye
Published: April 2011

ZnTe quantum dots (QDs) have been very attractive because of their potential applications in optoelectronic devices operating in the blue-green region of the spectrum. This paper describes a convenient one-step synthesis of high-quality ZnTe QDs in high-temperature organic solution with high yield. Anhydrous zinc chloride was dissolved in phenyl ether under argon protection and oleic amine was used as coordinating agent. Complex solution of metal tellurium in trioctylphosphine (TOP) was injected into the hot reaction mixture as a source of tellurium. The reaction was complete in several minutes and the resulting QDs were isolated by centrifugation and re-dispersed in hexane. The produced spherical ZnTe QDs are monodispersed and their sizes could be controlled simply by varying the growth temperature. The morphology and phase structure were investigated using TEM and XRD. Photoluminescence (PL) spectra were also studied and quantum size effects were observed as well.
AFM Studies on the Morphological Evolution of Chemically Deposited In2S3 Thin Films as a Function of Deposition Time
Authors: Sotelo-Lerma Merida , Castelo-Gonzalez Omar Armando , Ramirez-Bon Rafael , Espinoza-Beltran Francisco Javier
Published: April 2011

Indium sulphide (In2S3) is a very promising semiconductor material for window layers in solar cell devices. It is currently being investigated for high efficiency solar cell based on Cu(In,Ga)Se2-In2S3 heterostructures. The chemical bath deposition (CBD) technique is one of the most convenient methods to obtain In2S3 films because of its simplicity, low cost and some other advantages. Amorphous and polycrystalline In2S3 films on glass substrates have been obtained by the CBD technique. Like in many others CBD processes, the deposition mechanism and kinetic growth of In2S3 films on glass substrates is not very well understood [1-6]. In this work we have chemically deposited In2S3 films for different times from 6 up to 39 hours, in order to study by atomic force microscopy (AFM) the formation of the films on glass substrates. The AFM measurements were performed in a liquid medium in which the cantilever tip and the sample are completely immersed in the liquid. A specially designed AFM cell is composed of a tip attached to a circular transparent window, the liquid level is between the upper and lower surface of the window, and a circular meniscus is established around the window, preventing the tip could be affected or destroyed by the surface tension of the liquid. By using this liquid AFM technique, we can at real-time observe the thin film forming process, and thereby clearly reveal the growing mechanism. It is an ideal and more practical tool for in situ investigation of samples which are normally found in liquid environments.
Non-Contact Metrology for Electrical Characterization of Photo-Voltaic Materials
Authors: Current Michael Ira , Faifer Vladimir , Wong Tim , Walecki Wojtek , Nguyen Tan
Published: April 2011

A non-contact metrology for electrical characterization of p-n junctions has been developed for use on photo-voltaic materials. By analysis of junction photo-voltage (JPV) measurements at multiple light beam modulation frequencies and multiple light penetration depths, a comprehensive electrical analysis of photo-voltaic materials is provided for junction sheet resistance, leakage current, capacitance and bulk carrier diffusion length. The JPV analysis can be made with screen and native oxides on the surface, so no pre-measurement chemical etching is required. Since the probe does not contact the p-n junction surface, measurements can be made in a continuous fashion with the junction moving under the probe, providing a method for efficient high-resolution mapping of local electrical properties. The non-contact probing also allows for non-damaging measurements in both “hard” (Si) and “soft” (organic) photo-voltaic materials. Examples of p-n junction properties in polished, crystalline-Si and cast poly-Si will be discussed.
Characterization and Modeling of Transport and Interfacial Transfer of Electrons in Dye-Sensitized Solar Cells
Authors: Peter Laurence
Published: April 2011

Factors that determine the performance of dye-sensitized nanocrystalline solar cells are discussed
Development of YBCO film approached by TFA-MOD method using the Y2Ba1Cu1Ox and Ba3Cu5O8 powders
Authors: Lim Jun Hyung , Jang Seok Hern , Yoon Kyung Min , Joo Jinho , Jung Seung-Boo , Nah Wansoo
Published: April 2011

The YBCO films were fabricated by TFA-MOD method in route of ¡°211 process¡± and evaluated the phase formation, texture evolution, and critical properties as a function of the humidity firing process. In the fabrication process, Y2Ba1Cu1Ox and Ba3Cu5O8 powders, instead of Y-, Ba- and Cu-based acetates, were used as precursors. In order to evaluate the effect of humidity during the firing process, the films calcined at 430¡É were fired at 775¡É in dry Ar(0%), 4.2%, 8.0%, 12.1%, and 20.0% humidified Ar gas mixed with 1000 ppm oxygen.

We observed that the amount of BaF2 phase was effectively reduced and that a sharp and strong biaxial texture formed under a humidified atmosphere, leading to increased critical properties. The film became denser and the degree of texture and phase purity varied as the humidity increased. For the film fired in 0% humidity, the measured value of Tc(onset) was found to be 82.5 K, but the Tc(zero) could not be measured. When the humidity was increased to 4.2%, the corresponding Tc(onset) and Tc(zero) were increased to 91.5 K and 88.6 K, respectively. For the films in the humidity range of 12.1-20.0%, the critical current was found to be 30 A/cm-width (the corresponding critical current density is 1.54 MA/cm2).
New Macroporous Crosslinked Polymer Gels Prepared via Living Radical Polymerization
Authors: Kanamori Kazuyoshi , Nakanishi Kazuki , Hanada Teiichi
Published: April 2011

Macroporous crosslinked polymer gels have been prepared via TEMPO-mediated living radical polymerization of divinylbenzene (DVB) in a solvent with a counter polymer. Incorporating a counter polymer, poly(dimethylsiloxane) (PDMS), induced macroscopic spinodal-type phase separation during the course of polymerization of DVB while suppressing the segregation of DVB-derived particles from the solution by living polymerization. Well-defined macroporous morphologies comprising continuous DVB-derived skeletons have thus obtained. Macropore volume and diameter were independently controlled by altering the concentrations of PDMS and the solvent. Since the present polymer gels are prepared using only the multifunctional “crosslinker”, mechanical durability against bending and compression was found to be as high as inorganic ceramics with similar morphologies and porosities.
Polymer Adsorption onto Selective Mixed Brushes
Authors: Chervanyov Alexander , Heinrich Gert
Published: April 2011

We theoretically studied the reversible adsorption of polymers onto selective mixed brushes. Mixed brushes are recently developed self-adoptive materials that reversibly change their morphology in response to altering external stimuli. The above changes in the morphology result in the reversible formation of different patterns on the outer surface of the brush. It is shown that thus achieved patterning of the adsorbing surface of the mixed brush can dramatically enhance the adsorption of polymers onto this brush, as compared to the adsorption onto the homogeneous brush surface. By making use of the developed self-consistent field theory we calculate the surface excesses of homo- and co-polymers adsorbed on the binary mixed brush for the two different morphologies (`ripple' and random). The interplay between the depletion effect caused by the loss of the polymer entropy in the interior of the brush and binding interactions is shown to lead to a rich adsorption-desorption behavior. The surface excess of the adsorbed polymers is calculated as a function of the relation between the radius of gyration of the adsorbed polymers and characteristic size of the surface pattern. Shorter (relative to the size of the pattern) polymers are shown to better adsorb onto the regular patterned brush surface, as compared to the random brush surface.
A Simple Method to Grow Polymer Nanofibers from Superglue
Authors: Mankidy Pratik , Rajagopalan Ramakrishnan , Pantano Carlo , Foley Henry
Published: April 2011

A novel template-less method for polymerization of ethyl 2-cyanoacrylate to form an intrinsically nanofibrous polymer is investigated. Effect of the anionic initiator used for polymerization is examined to explain the mechanism of formation of nanofibers or film of polymer. A suitable classification of the initiators is established based on the Hard Soft Acid Base principle to explain the mechanism. Infrared analysis, SEM and Gel permeation chromatography is utilized for characterization of the different polymer samples.
Polyethylene Oxide Nanofibers as Ultraviolet Sensors
Authors: Khan Saima Naz , Rack Jeffrey J. , Rachford Aaron R. , Kordesch Martin E.
Published: April 2011

Using the electrospinning technique, we have prepared [Ru (pic) 2 (dmso) 2] doped-polyethylene oxide nanofibers for ultraviolet sensing. The diameter of the as-prepared fibers is in the range of 1μm-100nm. These fibers change color from pale yellow to orange when exposed to ultraviolet light (wavelength∼350nm) and return to their original color after approximately 2-3 days. The intensity of the color increases with an increased time of exposure to UV. The color changing behavior in the nanofibrous mat is almost the same as that in cast films prepared from the same solutions. The scanning electron microscope (SEM) studies of the fibers show that the morphology of the fibers remains unchanged after exposure to UV.
Formation of Palladium Structures Combining Electrospinning and dc Sputtering
Authors: Otaño Wilfredo , Otero Ariel O. , Otaño José M. , Otaño Carlo S. , Santiago Jorge J. , Pantojas Víctor M.
Published: April 2011

Electrospinning and dc sputtering techniques were combined for the formation of a variety of nano-to-microscale structures of palladium metal. Polyethylene fibers created by electrospinning were used as templates for the dc sputtering of palladium on top of them. Heating the fibers to 320 °C in air eliminated the central polymer core (fugitive phase) resulting in the formation of open and closed core fibers, depending on the amount of Pd previously deposited. The formation of the structures is best explained as a consequence of sputtering being a line-of-sigh technique. Palladium is preferentially sputtered on top of the fiber part facing the target, resulting in a non-uniform deposition. Furthermore, it is proposed that the deposition of palladium on top of the fibers results in the nucleation of palladium crystals growing outward of the surface and producing interesting nanoscale features observed resembling thorns and scales.
Electrical Bending and Mechanical Buckling Instabilities in Electrospinning Jets
Authors: Reneker Darrell H. , Han Tao
Published: April 2011

The determination of the behavior of the jet path in the vicinity of the onset of the primary electrical bending instability is important for the orderly collection of the nanofibers produced by electrospinning. A stable jet was observed with a high frame rate, short exposure time video camera. The collection process was complicated but predictable within limits, so the design and creation of some two or three dimensional structures of nanofibers is feasible, if the considerations described below are incorporated into the design and production processes.

The fluid jet in the straight segment of the path, and the more solid nanofibers in the coils of the primary electrical bending instability were collected on stationary and moving surfaces. The diameter and characteristic path of the jet depended on the exact distance between the orifice and the collector, if other parameters were not changed. The moving surfaces caused the various coils that were collected to be displaced rather than superimposed. The fiber collected on the moving surfaces preserved a record of the electrical and mechanical instabilities that occurred. If the straight segment was very fluid, the jet formed a series of small sessile drops on the collector, but when the jet was more solid, buckling occurred and produced small, complicated loops close to point at which the jet hit the surface. Buckling was observed during collection of the straight segment and the first coils of the electrically driven electrical bending instability. A moving inclined collector was used to collect the fibers. Surface velocities were up to about 5 meters per second. These velocities are commensurate with the velocities at which the solidifying jet approached the surface. A variety of structures of loops, both conglutinated and not, associated with the instabilities were created.

The jets used in this work were formed from solutions of polyethylene oxide, nylon-6, poly lactic acid, and other polymers. Several solvents were used for some of the polymers, and details of the jet path changed when the solvent or the concentration changed. The jets issued from a pendent drop on a glass capillary with an orifice diameter of about 160 microns. A potential difference in the range of 500 to 13,000 volts was applied between the orifice and the collector. The distance from the orifice to the grounded collector varied from 1 mm to 30 cm. Interference colors associated with jet diameters around 10 microns were observed in the straight segment. The color patterns were stable, indicating that the process variations were small.
Development of Novel Materials for Proton Exchange Membrane Fuel Cells
Authors: Birkan Burak , Levi Albert , Gümeci Cenk , Gülgün Mehmet Ali , Mencelo∂u Yusuf Ziya
Published: April 2011

The most known utilization of catalysts is the use of metal nanoparticles on the electrode of a Proton Exchange Membrane Fuel Cell on which the electrode consists of catalyst, either Pt or Pd on a carbon support. In this research porous polyacrylonitrile (PAN) based carbon nanofibers comprising nanosized metal particles are produced using electrospinning technique. By the optimization of polymer chemistry, electrospinning variables and carbonization procedures the effective metal size is reduced up to 5 nm. It is still possible to enhance the catalytic performance by decreasing the metal concentration and/or enable using less catalytic material for equivalent catalytic performance which can lead to cost savings, amongst other advantages.
Ferroelectric Polymers with Chemically Tunable Dielectric Constants
Authors: Lu Yingying , Claude Jason , Li Kun , Zhang Qiming , Wang Qing
Published: April 2011

We present a modular approach toward poly(vinylidene fluoride) based ferroelectric polymers with high dielectric constants and energy densities. This strategy is based on a two-step reaction including the co-polymerization of vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) and a subsequent hydrogenation reaction. Due to the similar reactivity of VDF and CTFE in free radical polymerization and quantitative yield of dechlorination reaction, the chemical compositions of the resulting terpolymers can be precisely controlled, leading to tunable Curie temperatures and dielectric constants. A library of the ferroelectric polymers with dielectric constants varying from 11 to 50 measured at 1 kHz and room temperature has been prepared. The structural characteristics including microstructure, chain conformation, and crystallinity of the polymers have been carefully elucidated as a function of the chemical composition by 1H and 19F NMR, Fourier transform infrared spectroscopy, and wide angle X-ray diffraction. The influence of the polymer compositions on thermal transitions and dielectric constants has also been investigated.
Dielectric Properties of CaCu3Ti4O12-P(VDF-TrFE) Composite
Authors: Shan Xiaobing , Yang Xin , Zhang Kewei , Cheng Zhongyang
Published: April 2011

By using conventional solution casting method, a flexible ceramic [CaCu3Ti4O12 (CCTO)]-Polymer [P(VDF-TrFE)] composite has been fabricated. The CCTO ceramic powders with a relative uniform size were prepared by traditional powder processing method. The dielectric properties of these films with different CCTO fractions were determined. The process was optimized to achieve high dielectric constant. A dielectric constant about 510 at room temperature and 1240 at 95 °C at 1 kHz for 6 layer hot compression was obtained.
Preparation and Surface Modification of Rare-Earth Doped Ceramic Nano-Phosphors for Fluorescence Bioimaging
Authors: Soga Kohei , Saito Yu , Shimizu Kazuaki , Nagata Hiroyasu , Konishi Tomoya , Nagasaki Yukio
Published: April 2011

Rare-earth doped yttrium oxide nano-particles modified with bio functional polymers are one of the good candidate for upconversion bio imager. The requirement to the particles for bio imaging application is a small particle size less than 50 nm, dispersion and chemical durability in body fluid. In this study, polyacrylic acid (PAAc) was used for both precursor precipitation and surface modification of the calcinated particles. The use of the PAAc resulted in small particle size at 33 nm. Also, the modification by adding 104 PAAc/particle resulted in chemical durability and dispersion of the particles under heavily acidic and basic conditions.
Graph Spectra of Carbon Nanotube Networks: Molecular Communication
Authors: Bush Stephen Francis , Li Yun
Published: April 2011

The integrated application within random carbon nanotube networks (CNT) to carry and fuse information, as well as perform simple sensing, is explored. One may imagine small CNT networks with functionalized nanotubes simultaneously sensing multiple targets in-vivo for unprecedented understanding of biological pathways. This is clearly distinct from the traditional convoluted approach of using CNT networks to construct transistors that are in turn used to construct communication networks. With random CNT network layouts, routing of information is an integral part of the physical layer.

A Mathematica analysis for evaluating random CNT networks has been developed and used to verify design characteristics. The graph spectrum of the CNT network is used to determine resistance and electron mobility characteristics. Thus, we have been able to find relationships among CNT network structure and electron mobility. The nanotube density allows for an increase in the number of bits per square meter of information transfer compared to wireless communication. Consider a wireless network; a typical bit-meters/second capacity is limited in a traditional wireless network. The maximum wireless capacity approximation in a wireless broadcast media is contrasted with a CNT network; we look at the efficiency of CNT networks to carry information and compare with theoretical limits.
DAPI Method: A Novel Assay to Evaluate the In vitro Impact of Nanomaterials on Mammalian Cells
Authors: Raja Pavan M. V. , Connolley Jennifer , Ajayan Pulickel M. , Nalamasu Omkaram , Thompson Deanna M.
Published: April 2011

The increasing importance of nanomaterial-related applications has given rise to concerns pertaining to their impact on human health. In vitro mammalian cell-based assays can provide a quick and simple estimate of the possible adverse effects of the nanomaterials. However, recent studies have questioned the efficacy of traditional assays such as the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, in evaluating cell-nanomaterial interactions, implying the need for alternate methods. We applied image analysis to enumerate the DAPI (2-[4-(Aminomethyl) phenyl]-1H-indole-6-carboximidamide, dihydrochloride) – stained cellular nuclei. Image analysis, being non-destructive, capable of automation, and applicable over a wide range of cell seeding densities, offers several advantages compared to older methods like the MTT assay and hemocytometry. Using image analysis, the impact of singlewalled carbon nanotubes (SWNT) on rat aortic smooth muscle cell (SMC) growth kinetics, were examined. Despite the carbon nanomaterial presence, the fluorescent signal from the nuclei was not noticeably impacted over the SWNT range examined (0.00-0.10 mg/ml). We anticipate that this method can also be applied to evaluate the biological impact of other nanomaterials.
Development of Au Nanowires for Recording Electrical Activity in Neural Cells
Authors: Silverberg Jesse , Saha Sucharita , O'Malley Donald , Menon Latika
Published: April 2011

The application of gold nanowire arrays for neuronal recording and stimulation is explored. The process of electrochemical anodization is utilized to grow an aluminum oxide template consisting of an array of closely packed cylindrical pores with diameters in the range of nanometers and micron scale depth. The method of electrodeposition is used to deposit gold within the pores forming a nanowire array. By means of micro and nanoscale fabrication processes, this array is integrated at one end with microscale gold electrodes. At the other end, neuron cells are cultured. Such nanowire-array structures will eventually be used to record and stimulate neuronal activity.