bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Modifications of CMR Manganite Thin Films Using Atomic Force Microscope
Authors: Schaefer David Matthew , Sneider Matthew , Bolling Cameron , Sunderland John , Davidson Anthony L. , Kolagani Rajeswari M. , Bradley Tyler , Ludka Bonnie , Hall Kyle
Published: April 2011

Reproducible nanoscale surface lithography have been produced on La00.66Ba0.33MnO3 thin films using Atomic Force Microscopy. Using an anodic oxidation technique, structures were produced using both positive tip bias voltages as well as negative tip voltages. The electric field produced by applying a positive tip bias acts to reduce the region near the surface, whereas negative tip bias causes an oxidation reaction. Using a positive tip bias, stable structures were consistently achieved which demonstrated a linear dependence of height and width on tip voltage and writing speed. Heights ranged from 5 – 50 nm and widths from 400 – 2000 nm. Negative bias voltages produced a rapid oxidation of the surface, resulting in uncontrollable writing. After etching with a 50% HCL solution it was found that controlled writing was possible with negative bias voltages.
Electrical Characteristics of BaxSr1-xTiO3(BST) Capacitors Implemented with Ti-Al Electrodes
Authors: Kalkur Thottam S , Whitescarver Jeff , Cramer Nick
Published: April 2011

Ti-Al was used as the electrode for RF magnetron sputtered BST film at a substrate temperature of 450°C for decoupling capacitor applications. X-ray diffraction analysis shows that the deposited film BST film is amorphous. Electrical characterizations of the devices performed by capacitance versus voltage measurements show a dielectric constant of about 55. With increase in annealing temperature above 450°C, the capacitance was found to decrease significantly.
Thermoelectric Properties of Nano-structure Controlled Sm2−xCexCuO4 Thin Films
Authors: Ichino Yusuke , Yamazaki Koji , Yoshikawa Tomoki , Yoshida Yutaka , Takai Yoshiaki
Published: April 2011

Sm2−xCexCuO4 (SCCO) is well known as an n-type superconductor with large physical anisotropies. In order to enhance the thermoelectric conversion performance, we have prepared the SCCO epitaxial films and controlled a crystallographic orientation, a carrier concentration and an introduction of nano-structures. The SCCO films and nano-structures consisting of CeO2 were fabricated using pulsed laser deposition method on SrTiO3 single crystalline substrates. Due to the orientation control and the optimization of carrier concentration, a low resistivity and a high Seebeck coefficient were achieved, and a power factor (PF) reached 1.14×10−3 W/mK2 at 323 K in the SCCO film with x × = 0.02. In addition, we measured the nano-structural effect on the PF of SCCO films. As a result, the PF showed a maximum in the film on a certain shape of the nano-structures. We speculate that the low resistivity was achieved by a formation of high Ce concentration layer near the interface between film and nano-structure.
Reversible Electrical Field-Induced Formation of Ruddlesden-Popper Phases in Strontium Titanate at Room Temperature
Authors: Meyer Dirk Carl , Levin Alexandr A. , Leisegang Tilmann , Gutmann Emanuel , Reibold Marianne , Paufler Peter , Pompe Wolfgang
Published: April 2011

On base of the structural characteristics of near-surface regions of a SrTiO3 (001) (STO (001)) single-crystal plate revealed by means of wide-angle X-ray scattering (WAXS), X-ray fluorescence spectroscopy and high-resolution transmission electron microscopy, structural changes in the STO (001) single-crystal plate under the influence of an external electric field at room temperature can be described as the tunable and reversible formation of Ruddlesden-Popper-phases of the quasi-binary system SrO-TiO2. The WAXS behavior implies the use of the reversible phase-transition for adaptive X-ray optics.
Carbon Nanotubes: Research and Instrumentation For Undergraduate Students
Authors: Dillingham T. Randy , Porter Tim , Vail Tim , Hartzell Cynthia , Sellers Marilee
Published: April 2011

A team of faculty at Northern Arizona University (a predominantly undergraduate institution) have joined forces to develop a cross-disciplinary course for sophomore level science students in nanotechnology and the associated instrumentation with an overarching theme centered around carbon nanotubes. Research laboratories with various analytical capabilities were utilized from the Departments of Biology, Chemistry, and Physics and Astronomy. Specifically, the techniques that were used included scanning electron microscopy, x-ray photoelectron spectroscopy, nuclear magnetic resonance, and micro-sensor technology. The course content, the student activities and the initial experience in developing and team-teaching the course are described.
The Nanoscience Undergraduate Education (NUE) Program at James Madison University
Authors: Augustine Brian H , Reisner Barbara A. , Caran Kevin L.
Published: April 2011

Work has been underway at JMU in the Department of Chemistry through an NSF-NUE grant to develop an evolutionary approach to curriculum development across the undergraduate chemistry curriculum. Preliminary assessment data suggests that there exists a profound misunderstanding amongst graduating chemistry majors about basic aspects of nanotechnology as revealed by the NAI. Specifically, there are misconceptions about the sizes of and forces acting on the molecular-scale which is fundamental to any deep understanding of nanometer-scale phenomena. This is particularly alarming since senior-level undergraduate students majoring in chemistry should have a clearer understanding of molecular interactions than other STEM disciplines. A more careful, coordinated and sustained approach to teaching nanometer-scale phenomena must be undertaken in order to address these misconceptions and better prepare students the future workforce in nanoscience and nanotechnology.
European Activities in Nanoscience Education and Training
Authors: Baraton Marie-Isabelle , Monk Raymond , Tomellini Renzo
Published: April 2011

This paper reviews salient features of the European initiatives to promote education in the field of nanosciences and nanotechnologies. Not only funding issues but also inherent cultural specificities are taken into account to evaluate the strengths and weaknesses of the European model to take up the challenge of the global economy. Multidisciplinarity and mobility of researchers appear to be key to foster excellence, whereas a reappraisal of curricula is necessary.
Influence of the Ge Dose in Ion-implanted SiO2 Layers on the Related Nanocrystal-memory Properties
Authors: Duguay Sébastien , Grob Jean-Jacques , Slaoui Abdelilah , Kern Philippe
Published: April 2011

Thin silicon dioxide (SiO2) on Si layers with embedded germanium nanocrystals (Ge-ncs) were fabricated using 74Ge+-implantation at 15 keV and subsequent annealing. Transmission electron microscopy and Rutherford backscattering spectrometry have been used to study the Ge redistribution in the SiO2 films as a function of implantation dose under specific annealing conditions. At low implantation doses, Germanium is found to segregate at the Si/SiO2 interface leading to poor electrical properties. At higher doses and when the disorder limit of one displacement per atom is reached at the interface, transmission electron microscopy revealed the formation of a Ge-nc layer array located close to the Si/SiO2 interface and an another one inside the SiO2 host material. This near-interface high density (>1012 ncs/cm2) nc-layer is found to act as a floating gate embedded within the silicon dioxide. Capacitance-voltage measurements performed on metal-oxide-semiconductor structures containing such implanted SiO2 layers show significant memory properties (few volts hysteresis) at low programming voltages (<|10V|) due to the presence of Ge-ncs near the Si/SiO2 interface
Combinatorial Studies for High Density Si and Ge Nanoparticle Arrays
Authors: Stanley Scott K. , Ekerdt John G.
Published: April 2011

A simple combinatorial approach for studying chemical and physical vapor deposition (CVD and PVD) nanoparticle growth is presented utilizing temperature and precursor flux gradients across sample surfaces. Large temperature gradients (450-700 °C) are induced covering the entire range of interest for most CVD and PVD processes. Precursor flux gradients may also be introduced simultaneously or separately using a tungsten cracking filament mounted on a translation arm. Theory and calibration experiments are explained and results from a study on Ge nanoparticle growth on HfO2 surfaces are presented and analyzed. This method drastically decreases experimental time required to investigate nanoparticle growth and identify optimum deposition conditions. Furthermore, this approach greatly facilitates preparation of library samples containing a wide range (several orders of magnitude) in variation of nanoparticle sizes, density, and composition for subsequent studies.
Thermo-Electrical Analysis of an Optoelectronic Modulator Integrated in a SOI Rib Waveguide Operating in the Gb/s Regime
Authors: Iodice Mario , Coppola Giuseppe , Zaccuri Rocco Cristian
Published: April 2011

Silicon is the most diffused material for microelectronic industry and, in recent times, it is becoming more and more widespread in integrated optic and optoelectronic fields. We present the thermo-electro-optical analysis of an integrated waveguide-vanishing-based optical modulator based on free-carrier dispersion effect, realizable on standard SOI wafer. The optical behavior is based on the vanishing of the lateral confinement in the rib region, and consequent cut-off of the propagating mode. Results show that an optical modulation depth close to 100% can be reached with a bandwidth of about 154 MHz. Smart electrical driving, that is an injection overdrive of a few volts for a very short time, allows to reach total ON-OFF switching time of about 860 ps. For that bias scheme the fall transient is then limiting the whole dynamic and the resulting bit rate in a pure digital modulation scheme is about 1.2 Gb/s
Fabrication and Characterization of Thin-Film Metal-Insulator-Metal Diode for use in Rectenna as Infrared Detector
Authors: Krishnan Subramanian , Bhansali Shekhar , Buckle Kenneth , Stefanakos Elias
Published: April 2011

Uncooled Infrared detectors with high sensitivity and shorter response times are preferred as through the wall detection device. An alternate approach for making these sensors, being pursued by us is to use the concept of rectenna with tunnel diodes. Successful fabrication of such high frequency switching diodes with antenna as detectors, offer a much faster response time than existing bolometer. This paper presents the fabrication and characterization of thin-film MIM diode for use in rectenna as an Infrared detector. MIM diodes operate on the basis of quantum mechanical phenomenon, i.e., when a sufficiently thin barrier (<5nm) is sandwiched between two electrodes, current can flow between them by means of tunnelling. This tunnelling probability increases with a decrease in the dielectric barrier height and the separation distance. The MIM diodes were fabricated with asymmetric electrodes with 1μm2 contact areas with cut-off frequency ∼0.1THz. The electrodes of the Ni-NiO-Cr MIM diodes have been fabricated through Photolithography, e-beam lithography, followed by conventional lift-off process. The dielectric layer (NiO) was deposited through plasma oxidation to obtain 2nm thin films. The composition and the thickness of the insulator layer are characterized by metrological tools like SEM and Spectroscopic Ellipsometer. The diode characteristics presented in this paper have been found to be stable and reproducible with the established fabrication conditions. Electrical behaviour (I-V) of the MIM junctions were investigated and compared with the theoretical tunnelling characteristics of the Ni-NiO-Cr MIM diodes. For devices with such non-linear electrodes, excellent agreement is obtained between the measured and the calculated result with the forward bias current as 0.8mA at 0.2V and the reverse bias current as −0.2mA at −0.2V.
NASICON-like phases in ScPO4-Na3PO4-Li3PO4 quasiternary system
Authors: Zhuravleva Mariya , Zakalyukin Ruslan , Fomichev Valeriy , Novoselov Andrey , Yoshikawa Akira , Fukuda Tsuguo , Zimina Galina
Published: April 2011

Phase formation in ternary system of complex Sc, Na and Li phosphates was studied at 950°C and synthesis of new phases of definite composition was carried out. Obtained samples were investigated with X-ray powder diffraction, infrared and impedance spectroscopy. Compositions of fields of homogeneity with the NASICON-like structure were discovered. Temperature dependency of ionic conductivity was measured.
Electrical Characterization of Polyfluorene-Based Metal-Insulator-Semiconductor Diodes
Authors: Yun M. , Arif M. , Gangopadhyay S. , Guha S.
Published: April 2011

Polyfluorenes (PFs) have emerged as a promising family of blue polymer light-emitting diodes (PLED) due to their high electroluminescence quantum yield. Metal-insulator-semiconductor (MIS) diodes are the two terminal analogues of thin film transistors sharing the same basic layer structure. We have investigated two different structures based on poly [9,9'-(di 2-ethylhexyl)fluorene] (PF2/6), a MIS diode and a hole-only PLED. The MIS diodes were fabricated with the PF2/6 layer on p+ Si /Al2O3 substrates, and were characterized by means of capacitance-voltage (C-V) measurements as a function of frequency. From C-V measurements, the unintentional doping density is evaluated as ∼5.7×1017 cm−3 at frequencies above 20 kHz. The interface trap density is estimated as ∼7.2×1011 eV−1cm−2 at 10 kHz. Current-voltage measurements of PF2/6-based PLEDs shows a shallow trap space-charge-limited conduction from which the energy of the traps and hole mobilities are estimated.
Design of a Passive-Matrix Smart Window by the Conjugated Polymer Electrochromics
Authors: Furukawa Rei , Xu Chunye , Taya Minoru
Published: April 2011

Preliminary development towards passive matrix Electrochromic (EC) device in conjugated EC polymer system is discussed. High contrast ratio of dark and bleached pixels is obtained by modification of counter and working electrode capacitance ratio and spacer geometry. Mask patterning and laminar electropolymerization for multicolor EC system application is discussed.
Probing Electronic Properties of dendritic Ruthenium Complex bound to Single Walled Carbon Nanotubes
Authors: Chaturvedi Harsh , Poler Jordan
Published: April 2011

We have functionalized single walled carbon nanotubes (SWNTs) using ruthenium centered organometallic supramolecular dendritic complexes. These dendrimers have multiple binding sites with chemically specified chirality. Most importantly, they are mechanically rigid. We have fabricated field effect transistors (FET) using these functionalized SWNTs. Devices were processed with standard optical lithography and high resolution e-beam lithography. We are using FET response of these devices to study charge injection into the nanotubes and the resultant effect on the tube's transport properties. Organometallic based molecular adsorbents onto the nanotubes effect the transistor response. These functionalized tubes change their majority carriers from holes to electrons in these FETs. We believe this is due to charge transfer from the metal center through the ligand and finally onto the nanotube. This results in the potential for optically altering the carrier density, and therefore the transport properties of the nanotubes.
Low-Temperature Solid-Phase Epitaxy of Defect-Free Aluminum p+-doped Silicon for Nanoscale Device Applications
Authors: Civale Yann , Nanver Lis K. , Hadley Peter , Goudena Egbert J. G. , van Zeijl Henk W. , Schellevis Hugo
Published: April 2011

A solid phase epitaxy (SPE) technique was developed to grow p+ aluminum-doped crystalline Si in a fully CMOS compatible process. This paper describes the experimental conditions leading to the selective growth of nanoscale single crystals where the location and dimensions are well controlled, even in the sub-100 nm range. The SPE Si crystals are defined by conventional lithography, show excellent electrical characteristics, and are uniform over the whole wafer. Fifty nanometer thick p+ SPE Si crystals were used to fabricate p+-n diodes and p+-n-p bipolar junction transistors. The high quality of the SPE Si and the remarkable control of the whole process, even in the sub-100 nm range, make this module directly usable for Si-based nanodevices.
How Many Fe layers Cause TMR?
Authors: Heiliger Christian , Zahn Peter , Mertig Ingrid
Published: April 2011

The influence of the structural properties of the leads of planar tunnel junctions on the tunneling current is investigated by means of ab initio electronic structure calculations. In particular, a NM/Fe/MgO/Fe/NM tunnel junction with non-magnetic (NM) leads and finite Fe spacer layers between the leads and the MgO barrier is discussed. The conductance is calculated as a function of the number of Fe layers. The results show that even one iron layer next to the barrier is sufficient to obtain a high spin polarization and a high TMR ratio. This finding implies that similar results can be expected for tunnel junctions with nonmagnetic and even amorphous leads, if states of Δ1 symmetry are provided.
Alloy Synthesis by Atomic Layer Laminations for Read Sensor Applications
Authors: Lee Chih-Ling , Devasahayam Adrian J , Mao Ming
Published: April 2011

A novel method has been developed for synthesis of multi-element alloys by planetary magnetron sputter deposition techniques. The alloy is formed by alternating depositions of uniform ultra-thin component layers at a fraction of a mono-atomic layer, or atomic layer lamination. A minimal layer thickness of down to 0.1Å can be obtained such that the components can be mixed at atomic level forming a homogeneous alloy.

A typical example is demonstrated here for the synthesis of CoxFe1−x alloys by alternating depositions of Co and Fe layers from pure element targets. The compositional dependence of the laminates basically reconstructs the well-known Slater-Pauling curve of the bulk CoxFe1−x alloys. The laminates exhibit a clear structural transition at Co compositions between 60 and 80 % from fcc phase to bcc phase, characteristic of bulk CoxFe1−x alloys. The novel atomic layer lamination has been successfully applied to the composition optimization of CoFe pinned layer with a best pinning strength at Co70Fe30 for exchange biased spin-valve films.
Controlled Synthesis of Zinc Selenide Nanostructures using Oil-Water-Amphiphilic Block Copolymer Liquid Crystals
Authors: Karanikolos Georgios N. , Alexandridis Paschalis , Mountziaris T. J.
Published: April 2011

A technique for simultaneous size and shape control of compound semiconductor nanostructures using poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) block copolymer/water/p-xylene lyotropic liquid crystals as templates is reported. Luminescent quantum dots of ZnSe were grown in the spherical domains of reverse (water-in-oil) cubic liquid crystals, hollow nanospheres and hollow nanotubes were grown around the dispersed spherical and cylindrical oil domains of the normal (oil-in-water) cubic and hexagonal phases respectively, and free-standing quantum wells (nanoplates or nanolaminates) were grown in the lamellar liquid crystals. The ZnSe nuclei were formed at room temperature by a spontaneous and irreversible reaction between zinc acetate that was dissolved in the water phase, and hydrogen selenide that was allowed to diffuse into the liquid crystalline templates. The nanostructures were characterized by HR-TEM, XRD, and optical spectroscopy. The shape of the nanocrystals can be controlled by selecting the structure of the templating phase. The size of the nanocrystals can be controlled by the size of the nanodomains and the concentration of the zinc precursor in them.
Sintering of Silver Nanoparticles for the Formation of High Temperature Interconnect Joints
Authors: Murray A. J. , Jaroenapibal P. , Koene B. , Evoy S.
Published: April 2011

We report the development of a metallic colloid sintering process enabling the creation of bonding layers at moderate temperatures ranging from 150°C to 300°C, and pressures lower than 5MPa. This colloidal n-propyl acetate dispersion of Ag nanoparticles, having an average size distribution of 103nm, was used in sintered interconnect fabrication. Open air sintering of a 10um thick film resulted in an average resistivity of 0.20·10−6 −0.30·10−6 Ωm. Film resistances were found to be as low as 0.18·10−6 Ωm. Independent test varying either pressure or temperature were correlated to ultimate shear strength and modulus. The analysis of a 1cm2 bond area resulted in a peak shear strength of 5.83 MPa and shear modulus of 346 MPa which occurred following bonding at 300°C with a pressure of 4.219 MPa.
Relaxation of Aggregates in a Jamming Colloidal Suspension After Shear Cessation
Authors: Ianni Francesca , Lasne David , Sarcia Regis , Hebraud Pascal
Published: April 2011

The reversible formation of aggregates in a shear thickening, concentrated colloidal suspension is investigated through speckle visibility spectroscopy, a dynamic light scattering technique recently introduced [1]. Formation of particle aggregates is observed in the jamming regime, and their relaxation after shear cessation is monitored as a function of the applied shear stress. The aggregate relaxation time increases when a larger stress is applied. Several phenomena have been proposed to interpret this behavior: an increase of the aggregate size, or a closer packing of the particles in the aggregates.

1. P.K. Dixon, D.J. Durian, Phys. Rev. Lett. 90, 184302 (2003).
Polydiacetylene Liposomes Attached to Glass Fibers for Fluorescent Bioassays
Authors: Reppy Mary A , Pindzola Bradford A
Published: April 2011

Polydiacetylene (PDA) is a conjugated polymer that changes its fluorescent state in response to environmental changes and can act as a transducer to convert molecular interactions into a discernable output measurable in the macroscopic world. Energy transfer to fluorophores can further enhance the fluorescent signal. Diacetylene liposomes can be prepared with phospholipids and other cell membrane components in the liposomes, and photopolymerized. PDA liposomes have been used for absorbance based detection of biological targets; however, moving to fluorescence detection gives increased sensitivity and also allows sensing from PDA structures deposited on opaque membranes. Unfortunately, PDA liposomes are prone to aggregation, particularly in the presence of divalent cations. Many enzymes require divalent cations such as Mg2+, Mn2+, Ca2+, etc., as co-factors; the tendency of PDA liposomes to aggregate in the presence of these cations limits their use as a platform for detection of enzymatic activity. We have developed methods for attaching PDA liposomes to glass fiber membranes, via thiol-epoxide coupling chemistry, for use in bio-assays and have seen that these materials can be used in place of PDA liposome solutions. We present here the attachment of PDA liposomes to glass fiber membranes in 96-well format, cryogenic TEM scans of the attached liposomes and the use of these materials in fluorescence assays to detect the activity and inhibition of phospholipase A2.
AC Loss Characteristics of Stacks of YBCO Coated Conductors
Authors: Grilli Francesco , Ashworth Stephen P. , Stavrev Svetlomir
Published: April 2011

Practical applications of YBCO coated conductors (CC) involving superconducting coils will utilize tapes packed together in an arrangement resembling a vertical stack. In such configuration there is an important electromagnetic interaction between the tapes, which strongly influences the loss characteristic of the device.

In the presence of an external magnetic field, the losses are reduced compared to an isolated tape because of the reduced aspect ratio of the conductor and, at least for low fields, because of an effective screening of the central part of the stack. On the contrary, in the case of AC transport current, the losses tend to increase due to the enhancement of the local field caused by the interaction of the self-field produced by neighboring tapes. In practical situations the conductor is usually subjected to both transport current and magnetic field, so that there is a trade-off between the two effects.

In this paper we investigate, both experimentally and by means of finite-element method calculations, the ac loss behavior of a stack composed by a finite number of tapes in different working conditions, and we compare the AC losses to the ones of non-interacting tapes in order to determine if the use of stacked tapes is advantageous from the point of view of power dissipation.
Stretched Polymer Nanohairs by Tailored Capillarity and Adhesive Force
Authors: Jeong Hoon Eui , Lee Sung Hoon , Kim Pilnam , Suh Kahp Y.
Published: April 2011

We present a simple method for fabricating high aspect-ratio polymer nanostructures on a solid substrate by sequential application of molding and drawing of a thin polymer film. In this method, a thin polymer film is prepared by spin coating on a solid substrate and the temperature is raised above the polymer¡¯s glass transition while in conformal contact with a poly(urethane acrylate) (PUA) mold having nano-cavities. Consequently, capillary forces induces deformation of the polymer melt into the void spaces of the mold and the filled nanostructure was further elongated upon removal of the mold due to tailored adhesive force at the mold/polymer interface. The optimum value of the work of adhesion at the mold/polymer interface ranged from 0.9 to 1.1 times that at the substrate/polymer interface. Below or above this range, a simple molding or detachment occurred, corresponding to earlier findings.
Coaxial Electrospinning for Nanostructured Advanced Materials
Authors: Loscertales Ignacio G. , Díaz Gómez Juan E. , Lallave M. , Rosas J. M. , Bedia Jorge , Rodríguez-Mirasol J. , Cordero T. , Marquez M. , Shenoy S. , Wnek G. E. , Thorsen T. , Fernández-Nieves A. , Barrero A.
Published: April 2011

Electro-hydro-dynamic (EHD) compound jets, with diameters in the micro and nanometric size range, from conical menisci of two co-flowing liquids, is a consolidated platform for the production of nanofibers with inner structure, in a process so-called coaxial electrospinning or co-electrospinning. In contrast to other multi-step template based procedures, the EHD methodology is much more simple and general since, firstly, a solid template is needless and, secondly, the process is seldom affected by the chemistry of the liquids. This gentle process allows selecting the liquid precursors depending on the application sought for the nanofibers. Here, we review different products obtained by this EHD technique: (1) solid and hollow carbon nanofibers from different precursors (polyacrylonitrile, polyvinylpyrrolidone and lignin), (2) nanofibers of biocompatible polymers encapsulating liquids in the form of beads, (3) spinning nanofibers of alginate and (4) in-fiber encapsulation of active microgels.
Effect of Strain Rate on the Mechanical Behavior of 10-micron Long Polymeric Nanofibers
Authors: Naraghi Mohammad , Chasiotis Ioannis , Dzenis Yuris , Wen Y. , Kahn Hal
Published: April 2011

The strain rate mechanical behavior of 12-micron long polymeric nanofibers was investigated. Experiments were carried out by a novel method that employs a MEMS-based leaf spring load cell attached to a polymeric nanofiber that is drawn with an external PZT actuator. The elongation of the fiber and the deflection of the load cell were calculated from optical microscopy images by using Digital Image Correlation (DIC) and with 65 nm resolution in fiber extension. The nanofibers were fabricated from electrospun polyacrylonitrile (PAN) with MW = 150,000 and diameters between 300-600 nm. At strain rates between 0.00025 s−1 to 0.025 s−1 the fiber ductility scaled directly with the rate of loading while the tensile strength was found to vary non-monotonically: At 0.00025 s−1 material relaxations allowed for near-uniform fiber drawing with up to 120% ductility and 120 MPa maximum tensile strength. At the two faster rates the tensile strength scaled with the rate of loading but the fiber ductility was the result of a cascade of localized deformations at nanoscale necks with relatively constant wavelength for all fiber diameters.
Polarized Luminescence from Single Polymer Nanowires and Aligned Nanowire Arrays
Authors: O'Carroll Deirdre , O'Riordan Alan , Redmond Gareth
Published: April 2011

The synthesis of poly(9,9-dioctylfluorene) conjugated polymer nanowires using the method of solution assisted wetting of nanoporous alumina membrane templates is reported. Polymer nanowires (approx. 109 per template) with a diameter of approx. 200 nm are obtained. Photoluminescence from isolated nanowires fluidically-aligned at glass substrates is found to be dominated by emission from the planar beta-phase of the polymer. The wires also exhibit polarized light emission suggestive of axial alignment of beta-phase segments within the nanowires. Dense arrays of aligned nanowires exhibiting anisotropic emission are also demonstrated.
Influence of Particle Size and Thickness of Material on Anti-voltage Strength of Energy-storage Composite
Authors: Luo Dabing , Guo Yan , Hua Hao , Liu Hanxing , Ouyang Shixi
Published: April 2011

After combining the PVDF and BST powders with different particle sizes, the anti-voltage strengths of composites was tested. Although the concentrates of ceramic were all the same, their anti-voltage strengths were distinguished. The results showed that the bigger particles or less thickness of material could benefit to the anti-voltage strength and ultimately enhanced the energy storage density of composites. Moreover, the distribution of particle dimension also influenced the strengths of materials. Composite with homogeneous particles performed higher strength than that of composites with inhomogeneous particles.
Influence of the Crystallisation Kinetics on the Microstructural Properties of α-PVDF
Authors: Silva Marco Pinto , Sencadas Vitor , Rolo Anabela G , Botelho Gabriela , Machado Ana Vera , Lanceros-Mendez Senentxu
Published: April 2011

The kinetics of the isothermal crystallization from the melt at different crystallisation temperatures and the melting behaviour of Poly(vinylidene fluoride) (PVDF) in the alpha phase has been investigated. The variation of the microstructure of the samples crystallized at different temperatures was monitored with time by Optical Microscopy. The correlation between microstructure and kinetic parameters allows the tailoring of the microstructure by choosing the crystallisation conditions of the samples. Raman and Infrared Transmission Spectroscopy also show the appearance of the γ-phase for higher crystallisation temperatures. The influence of the crystallisation kinetics on the degree of crystallinity of the samples will be also presented and discussed.
Sensitive Impurity Detection and Recognition in Inert Gaseous Media with SnO2 Based Gas Sensor Microarray
Authors: Goschnick Joachim , Schneider Thomas
Published: April 2011

Contrary to the conventional use of semi-conductive metal oxides as gas detectors for components in air the analytical performance of segmented SnO2-layers were investigated to detect and discriminate impurities in inert gases such as nitrogen or helium. A broad variety of technical processes require high purity inert gases which have to be kept under permanent surveillance to detect leaks to the atmosphere, a gas release of contaminated fittings or other contaminations. The unique gradient gas sensor microarray of the Karlsruhe micronose (KAMINA) was equipped with segmented layers of either nanoparticle or sputtered SnO2 layers and exposed to a high purity nitrogen flow of 1lit/min into which temporarily model impurities have been admitted with a variety of concentrations. Pulsed exposures were performed to nitrogen containing oxygen (0.2 to 10 vol %), water vapour (5 to 15 % relative humidity) and 2-propanol as well as tetrachloromethane in the ppm range. For all model contaminations a fast and sensitive response has been found. The measured concentration dependence revealed a detection limit of about 0.01 vol% for oxygen and 0.03% of relative humidity for an operating temperature of the KAMINA chip at 325..273 °C. The detection limits for the organic compounds were even found to be in the lower ppb range. The conductivity patterns obtained from the simple segmentation microstructure of the KAMINA SnO2 layers operated with a temperature gradient were evaluated by a Principal Component Analysis (PCA) which proved an appropriate gas discrimination power to distinguish pure nitrogen and the different kinds of contaminations for both types of SnO2 layers. However, the sputtered layer showed better detection limits while the nanoparticle layers offered a better sensitivity, i.e. a higher slope of the concentration dependence.
Synthesis and Characterization of Tunable and Highly Transparent Thick Layers of Nanocomposites Based on Methacrylates and Silica Nanoparticles
Authors: Simone Giuseppina , Perozziello Gerardo , Tagliaferri Vincenzo , Szita Nicolas
Published: April 2011

We present a nanocomposite material based on functionalized silica nanoparticles in a methacrylate matrix. The nanocomposite material is synthesized without addition of a co-solvent, which enables the spin-coating of thick and defect-free layers of several tens of micrometers with smooth surfaces. SEM analysis indicates uniform distribution of the nanoparticles in the methacrylate matrix, and pinhole-free surfaces suitable for applications in optics. For optical characterization, the refractive index of the material for different silica concentrations is reported, and propagation losses in the UV/VIS range discussed. The tuning of the refractive indices can be applied towards the realization of low-loss passive optical waveguides. As a first step towards this goal, the processibility of the nanocomposite material for microfluidic applications, and the realization of a planar optical waveguide are demonstrated.
Laser Deposited Ag3SbS3 and Tl3SbS3 Nanoscale Thin Films as Potential Electric Field Sensors
Authors: Khlyap Halyna , Panchenko Lyudmila , Laptev Victor , Shkumbatiuk Petro , Bilozertseva Violetta
Published: April 2011

Phase composition and electrical properties of Ag(Tl)SbS amorphous films obtained by pulse laser deposition technology are investigated. The films deposited on crystalline NaCl and Kcl substrates are amorphous with crystalline phase inclusions. Room-temperature current voltage characteristics showed a good electro-sensitivity of the films under applied bias up to 10 V and a space-charge-limited current was registered as a principal component of the charge carrier transport.
Effects of Post Calcination Treatment on Photoluminescence and Structural Properties of Scheelite-type LiEuW2O8Nanocrystals Synthesized by Glycothermal Reaction
Authors: Kasuya Ryo , Isobe Tetsuhiko , Yamao Shinobu , Sfihi Hocine
Published: April 2011

The scheelite-type LiEuW2O8(LEW) nanoparticles of ∼50 nm in diameter were synthesized from lithium acetate, europium (III) acetate and phosphotungstic acid in 1,4-butylene glycol at 300°C for 2h by autoclave treatment. Post calcination treatment at 600°C for 2 h enhanced the photoluminescence at 465 nm due to the 4f - 4f transition excitation of Eu3+by a factor of 24.4, and due to charge transfer (CT) excitation from either O2−or WO42−to Eu3+by a factor of 5.8. Convergent beam electron diffractmetry and the compositional analysis revealed the non-stoichiometric structure of the scheelite-type LEW nanocrystals. Raman spectroscopy also detected the WO4vibrational modes due to the tetragonal scheelite-type LEW. Solid-state7Li single pulse excitation MAS NMR indicated the existence of at least three Li sites in the samples. We conclude that the following three factors are improved by calcination to increase the f-f transition probability of Eu3+: (i) a distribution of the Eu3+– Eu3+distance, (ii) the symmetry of Eu3+polyhedra, (iii) the symmetry of tetrahedral WO4units in the vicinity of Eu3+polyhedra. Furthermore, oxygen is provided for non-stoichiometric LEW during calcination to enhance the CT probability.
Interactions of Carbon Nanomaterials With Mammalian Cells
Authors: Raja Pavan M. V. , Connolley Jennifer , Ci Lijie , Ganesan Gopal P. , Ajayan Pulickel M. , Nalamasu Omkaram , Thompson Deanna M.
Published: April 2011

Despite their diverse application potential, carbon nanotubes (CNT) have adverse effects in vitro, and in vivo. Previous research has focused on the in vitro cytotoxic impact of CNT aggregates and associated nanoparticulate impurities. In this study, we compared the single-walled carbon nanotube (SWNT) aggregates, and their associated finely dispersed, non-aggregated carbon nanomaterials on rat aortic smooth muscle cells (SMC), through filtration of the aggregates from the CNT-treated cell culture media. In general, our research shows that the removal of single-walled carbon nanotube (SWNT) aggregates from cell culture test media inhibited the growth in SMC to a lower extent than the corresponding unfiltered media at pre-filtered SWNT dosages below 0.10 mg/ml. We also found suspended nanoparticles (likely amorphous and graphitic carbon associated with the SWNT) and a small quantity of SWNT in the filtered media may have contributed to the observed cell growth inhibition by the filtered media. In addition, we compared the effect of SWNT, a nano-sized material, with activated carbon (AC), a nanoporous, microparticulate material, on SMC growth. AC (0.1 mg/ml) was found to be less inhibitory to SMC growth than the SWNT aggregates and suspended matter (0.1 mg/ml), potentially implying an inverse proportionality between carbon nanomaterial size regimes and cell growth inhibition.
Spherical Carbon Nanostructures - A Versatile Material for Sensing and Energy Storage
Authors: Friedel Bettina , Greulich-Weber Siegmund
Published: April 2011

Monodisperse smooth carbon nanospheres were synthesized via preparation and complex subsequent multistage pyrolysis of spherical melamine formaldehyde copolymer microparticles. The diameters of optained carbon spheres were located between several tens to several hundreds nanometers depending on the size of used initial copolymer particles. During the conversion of copolymer to carbon, the spheres pass strong shrinking of more than 80 % without any deformation. They meet the high quality standards of common prepared and used polymer and silica spheres and are therefore a promising material with great potential. Carbon nanoparticles could be used in a wide range of applications, such as for gas storage, fuel cells, sensing, catalyst support, separation and purification, supercapacitors or lithium-ion batteries, and photonic bandgap materials. Especially for the last mentioned usage monodispersity and a perfect spherical shape are very important. So-called synthetic opals from carbon spheres have been grown by sonic-supported sedimentation and a photonic bandgap in the infrared region has been found. Due to their high thermal resistance under non-oxidizing conditions carbon opals are also suitable as template for inverse opals. The structure of the spheres has been studied during different stages of carbonization by scanning electron microscopy, nuclear magnetic resonance and fourier transform infrared spectroscopy.
Highly Sensitive Surface Plasmon Resonance Sensor on Nanoscale Bioactive Surfaces for Specific Detection of Tri-Nitro Toluene
Authors: Singh Praveen , Onodera Takeshi , Matsumoto Kiyoshi , Miura Norio , Toko Kiyoshi
Published: April 2011

A nano-scale biosensor chip surface was fabricated using dinitro-phenylated key hole limpet (DNP-KLH) protein conjugate as ligand supported by underlying 11-amino 1-undecanethiol hydrochloride(AUT) self assembled monolayer (SAM) and bis sulfosuccinimidyl suberate(BS3) as crosslinker. Bioactive thin films were fabricated over gold chip via layer-by-layer self assembly methods. Biomolecular interaction between substrate specific anti-TNT antibody and DNP-KLH conjugate surface was monitored through surface plasmon resonance based optical sensor. The quantitation of tri-nitro toluene(TNT) on this bioactive surface was done using the solution based competitive inhibition assay. The DNP-KLH surface biosensor has shown a detection limit of 0.14 ng/ml(140 ppt) for TNT molecule. The detection limit of surface plasmon resonance(SPR) biosensor was further enhanced by using goat anti mouse antibody to the 0.002 ng/ml for TNT analyte. This TNT specific biosensor holds the promise to be one of most sensitive sensor surface under indirect competitive assay format. A short injection (12 sec) of 10 mM Glycine-HCl solution was found adequate for regeneration of DNP-KLH surface for repeated use.
Electrochemical synthesis of a ZnO nanowire field-effect transistor
Authors: Wade Travis Lee
Published: April 2011

Aluminum wires are electrochemically sculptured into bi-directional templates for the growth and contacting of nanowires as three terminal devices. The utility of this nanostructured micro-template is demonstrated by a ZnO nanowire surrounding gate field-effect transistor. This bottom-up approach to a 3-D nanowire transistor is unique in that it can be almost entirely fabricated in a beaker using aqueous, room-temperature electrochemistry.
Cytotoxicity of the Functionalized Gold and Silver Nanorods
Authors: Kuo Chiung-Wen , Lai Jun-Jung Lai , Chen Peilin
Published: April 2011

The cytotoxicity of various surface functionalized gold and silver nanords was measured by MTT assays for two cell lines, fibroblast and HeLa. It was found that the functionalized nanorods with 200 nm diameter and length up to a few micrometer can be readily internalized by both types of cells regardless of the surface functionalization. However, the cytotoxicity of the nanorods was found to depend on the polarity of the surface charge. The positively charged amino end group on the nanorod surface was found to be the least toxic whereas the negatively charged carboxylic acid end group on the nanorod surface caused lots of cell death. In general, the functionalized nanorods were found to be more toxic than the serum coated nanorods.
Functional Patternings Fabricated using Molecularly Imprinted Polymer; Molecular Recognitions for Chemical Detection
Authors: Choi Kyung
Published: April 2011

We present functional patterns fabricated using functional polymers. The functional polymer is MIP (molecularly imprinted polymer) system, which can be produced through “molecular imprinting” to create “synthetic receptor or binding sites” for bio/chemical detection technology. Those binding sites have specific molecular recognition functions for targeting organic or bio molecules. MIP's patterns in the micro-scale were fabricated for chemical sensors, diagonostic bio-sensors, and for drug delivery systems. We also obtained homogeneous MIP's micro-particles, which have high affinity receptor sites only using a microfluidic reactor.
Detection of Cell Surface Protein with Surface Enhanced Raman Spectroscopy
Authors: Tay Li-Lin , Hu Qingyan , Noestheden Matthew , Pezacki John
Published: April 2011

In this study, HeLa cells were transfected to express a recombinant transmembrane domain of the platelet-derived growth factor receptor. Silver nanoparticle (Ag-NP) functionalized with terminal hydrazide was employed to specifically target the ketone-conjugated cell surface proteins. In addition, a nitrile functional group was incorporated onto the Ag nanoprobe to provide unique vibrational signature (∼ 2230 cm−1) in a window which is free from other cellular components. The designed Ag nanoprobe functions as both recognition and transduction elements in the detection of the expressed cell surface protein. Scanning electron microscopy and surface enhanced Raman spectroscopy (SERS) imaging of the nanoparticle (NP) labeled HeLa cells revealed that all the observed intense SERS signals originated from aggregated NPs. Although isolated Ag-NPs is capable of SERS enhancement, its enhancement factor is beyond the detestability of such imaging experiments. The results have implication in the future design of SERS nanosensors for in vivo detection application.
Nanogap Capacitors Used for Impedance Characterization of Living Cells
Authors: Padmaraj Divya , Zagozdzon-Wosik Wanda , Miller John H. , Charlson Joe , Trombetta Len
Published: April 2011

Nano-gap metal oxide semiconductor (MOS) capacitors were studied to evaluate their limitations in applications of dielectric spectroscopy in living cells. The purpose was to optimize the design of a transducer to avoid interfacial polarization at the electrodes. Silicon IC technology was selected for designing processes in which we could limit electric double layer impedance by precisely controlling dielectric thickness of the capacitors in the range of 17 to 150 nm. The working capacitance was defined by lateral oxide etching of capacitor structures of various configuration to ensure high perimeter to area ratio. Highly doped n+ polysilicon and n+ implanted Si substrate were acting as capacitor's electrodes. Restrictions known from CMOS circuits regarding oxide leakage current, which depends on geometry and increases with the gate area were taken into account. To allow for testing cells (yeasts), which have larger dimensions than nano structures it was necessary to include cell manipulation using dielectrophoresis (DEP). Entrapment of cells at the electrode perimeter preceded electrical measurements. Our focus in analyses was on the frequency dependence of impedance parameters.
Optical Properties of Zn0.46Cd0.54Se/Zn0.24Cd0.25Mg0.51Se Multiple Quantum Wells for Infrared Photodetector Applications
Authors: Zhou Xuecong , Zhang Shengkun , Lu Hong , Shen Aidong , Wang Wubao , Song Chunying , Liu Huichun , Das Bidyut B. , Okoye Nicky , Tamargo Maria C. , Alfano Robert R.
Published: April 2011

Recently, lattice-matched Zn0.46Cd0.54Se/ZnCdMgSe multiple-quantum-wells (MQWs) have been recognized as very promising materials to fabricate intersubband (ISB) devices such as quantum cascade lasers and mid-infrared photoconductors. These structures have important applications in biological and chemical detections. The ISB transition covers a wide mid-infrared wavelength range from 1.3 μm to a few tens of μm.

In this work, two heavily doped n-Zn0.46Cd0.54Se/Zn0.24Cd0.25Mg0.51Se MQW structures have been grown on InP (001) substrate by molecular beam epitaxy. Temperature dependent steady-state photoluminescence (SSPL), temperature dependent time- resolved photoluminescence (TRPL), and Fourier transform infrared spectroscopy (FTIR) were performed to characterize their interband and ISB properties. These two MQW samples have similar structures except different well widths and different number of periods. The integrated SSPL intensities and the PL decay times of the MQWs were measured as functions of temperature in the range from 77 K to 290 K. The luminescence efficiency of the sample with 28 Å well width is larger than that of the sample with 42 Å well width although both samples exhibit similar temperature dependence of PL intensity. Time-resolved PL measurements show that the PL decay times of both samples decrease with increasing temperature. From 77 K to 290 K, the decay time of the sample with 28 Å well width is in the range of 440 ps ∼ 120 ps and is much longer than that of the sample with 42 Å well width, which is in the range of 65 ps ∼ 25 ps. Strong non-radiative recombinations dominate the luminescence behavior of the wider MQWs. Intersubband absorption spectra of the samples were measured by FTIR and show peak absorption at wavelengths of 3.99 μm and 5.35 μm for the MQWs with well widths of 28 Å and 42 Å, respectively, falling within the 3-5 Åm range, which is of great interest for the infrared photodetector applications.